Standardized module structure (FuelLabs#4232)

## Description

Implement RFC 0006, fix FuelLabs#4191.

Remove the `dep` reseved keyword in favor of `mod`.

Change path resolution for submodules to use an adjascent file at the
root and a folder named after the current module in other cases.

Remove the need for an argument to `library`, the LSP now points to
empty spans at the top of module files.

The library names are now determined by the file name, or the package
name at the top level.

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

docs/book/src/advanced/traits.md

@@ -77,7 +77,7 @@ ABI supertraits are intended to make contract implementations compositional, all
 Often, libraries and APIs have interfaces that are abstracted over a type that implements a certain trait. It is up to the consumer of the interface to implement that trait for the type they wish to use with the interface. For example, let's take a look at a trait and an interface built off of it.
 
 ```sway
-library games;
+library;
 
 pub enum Suit {
     Hearts: (),

docs/book/src/sway-program-types/libraries.md

@@ -7,17 +7,17 @@ Libraries in Sway are files used to define new common behavior. The most promine
 Libraries are defined using the `library` keyword at the beginning of a file, followed by a name so that they can be imported.
 
 ```sway
-library my_library;
+library;
 
 // library code
 ```
 
 A good reference library to use when learning library design is the [Sway Standard Library](../introduction/standard_library.html). For example, the standard library offers an [implementation](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/option.sw) of `enum Option<T>` which is a generic type that represents either the existence of a value using the variant `Some(..)` or a value's absence using the variant `None`. The [Sway file implementing `Option<T>`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/option.sw) has the following structure:
 
-- The `library` keyword followed by the name of the library:
+- The `library` keyword:
 
 ```sway
-library option;
+library;
 ```
 
 - A `use` statement that imports `revert` from another library _inside_ the standard library:
@@ -63,34 +63,48 @@ name = "my_library"
 
 which denotes the authors, an entry file, the name by which it can be imported, and any dependencies.
 
-For large libraries, it is recommended to have a `lib.sw` entry point re-export all other sub-libraries. For example, the `lib.sw` of the standard library looks like:
+For large libraries, it is recommended to have a `lib.sw` entry point re-export all other sub-libraries.
+
+The `mod` keyword registers a submodule, making its items (such as functions and structs) accessible from the parent library.
+If used at the top level it will refer to a file in the `src` folder and in other cases in a folder named after the library in which it is defined.
+
+For example, the `lib.sw` of the standard library looks like:
 
 ```sway
-library std;
+library;
 
-dep block;
-dep storage;
-dep constants;
+mod block;
+mod storage;
+mod constants;
+mod vm;
 // .. Other deps
 ```
 
-with other libraries contained in the `src` folder, like the block library (inside of `block.sw`):
+with other libraries contained in the `src` folder, like the vm library (inside of `src/vm.sw`):
 
 ```sway
-library block;
+library;
 
-// Implementation of the `block` library
+mod evm;
+// ...
 ```
 
-The `dep` keyword in the main library includes a dependency on another library, making all of its items (such as functions and structs) accessible from the main library. The `dep` keyword simply makes the library a dependency and fully accessible within the current context.
+and it's own sub-library evm located in `src/vm/evm.sw`:
+
+```sway
+library;
+
+// ...
+```
 
 ## Using Libraries
 
 There are two types of Sway libraries, based on their location and how they can be imported.
 
 ### Internal Libraries
 
-Internal libraries are located within the project's `src` directory alongside `main.sw` as shown below:
+Internal libraries are located within the project's `src` directory alongside
+`main.sw` or in the appropriate folders as shown below:
 
 ```bash
 $ tree
@@ -99,16 +113,18 @@ $ tree
 ├── Forc.toml
 └── src
     ├── internal_lib.sw
-    └── main.sw
+    ├── main.sw
+    └── internal_lib
+        └── nested_lib.sw
 ```
 
 As `internal_lib` is an internal library, it can be imported into `main.sw` as follows:
 
-- Use the `dep` keyword followed by the library name to make the internal library a dependancy
+- Use the `mod` keyword followed by the library name to make the internal library a dependancy
 - Use the `use` keyword with a `::` separating the name of the library and the imported item(s)
 
 ```sway
-dep internal_lib; // Assuming the library name in `internal_lib.sw` is `internal_lib`
+mod internal_lib; // Assuming the library name in `internal_lib.sw` is `internal_lib`
 
 use internal_lib::mint;
 

docs/reference/src/code/examples/fizzbuzz/src/lib.sw

@@ -1,4 +1,4 @@
-library fizzbuzz;
+library;
 
 // ANCHOR: state
 enum State {

docs/reference/src/code/language/built-ins/arrays/src/lib.sw

@@ -1,4 +1,4 @@
-library arrays;
+library;
 
 // ANCHOR: syntax
 fn syntax() {

docs/reference/src/code/language/built-ins/booleans/src/lib.sw

@@ -1,4 +1,4 @@
-library booleans;
+library;
 
 // ANCHOR: syntax
 fn returns_true() -> bool {

docs/reference/src/code/language/built-ins/bytes/src/lib.sw

@@ -1,4 +1,4 @@
-library bytes;
+library;
 
 fn syntax() {
     // ANCHOR: syntax

docs/reference/src/code/language/built-ins/enums/src/basic_enum.sw

@@ -1,4 +1,4 @@
-library basic_enum;
+library;
 
 // ANCHOR: definition
 enum Color {

docs/reference/src/code/language/built-ins/enums/src/enum_of_enums.sw

@@ -1,4 +1,4 @@
-library enum_of_enums;
+library;
 
 // ANCHOR: content
 enum UserError {

docs/reference/src/code/language/built-ins/enums/src/enum_of_structs.sw

@@ -1,4 +1,4 @@
-library enum_of_structs;
+library;
 
 // ANCHOR: content
 struct Item {

docs/reference/src/code/language/built-ins/enums/src/main.sw

@@ -1,4 +1,4 @@
-library enums;
+library;
 
-dep basic_enum;
-dep enum_of_structs;
+mod basic_enum;
+mod enum_of_structs;

docs/reference/src/code/language/built-ins/numerics/src/lib.sw

@@ -1,4 +1,4 @@
-library numerics;
+library;
 
 fn syntax() {
     // ANCHOR: syntax

docs/reference/src/code/language/built-ins/strings/src/lib.sw

@@ -1,4 +1,4 @@
-library strings;
+library;
 
 fn explicit() {
     // ANCHOR: explicit

docs/reference/src/code/language/built-ins/structs/src/lib.sw

@@ -1,4 +1,4 @@
-library structs;
+library;
 
 // ANCHOR: definition
 struct Foo {

docs/reference/src/code/language/built-ins/tuples/src/lib.sw

@@ -1,4 +1,4 @@
-library tuples;
+library;
 
 fn syntax() {
     // ANCHOR: declare

docs/reference/src/code/language/comments/src/lib.sw

@@ -1,4 +1,4 @@
-library comments;
+library;
 
 fn comment() {
     // ANCHOR: comment

docs/reference/src/code/language/control_flow/src/lib.sw

@@ -1,4 +1,4 @@
-library control_flow;
+library;
 
 fn conditional() {
     // ANCHOR: conditional

docs/reference/src/code/language/functions/src/explicit.sw

@@ -1,4 +1,4 @@
-library explicit;
+library;
 
 // ANCHOR: main
 fn main() -> bool {

docs/reference/src/code/language/functions/src/implicit.sw

@@ -1,4 +1,4 @@
-library implicit;
+library;
 
 // ANCHOR: main
 fn main() -> bool {

docs/reference/src/code/language/functions/src/lib.sw

@@ -1,7 +1,7 @@
-library functions;
+library;
 
-dep explicit;
-dep implicit;
+mod explicit;
+mod implicit;
 
 // ANCHOR: definition
 fn my_function(my_parameter: u64 /* ... */) -> u64 {

docs/reference/src/code/language/program-types/contracts/interface/src/lib.sw

@@ -1,4 +1,4 @@
-library interface;
+library;
 
 abi Wallet {
     /// When the BASE_ASSET is sent to this function the internal contract balance is incremented

docs/reference/src/code/language/program-types/libraries/external/my_library/src/lib.sw

@@ -1,4 +1,4 @@
-library my_library;
+library;
 
 use my_other_library::quix;
 

docs/reference/src/code/language/program-types/libraries/external/my_other_library/src/lib.sw

@@ -1,3 +1,3 @@
-library my_other_library;
+library;
 
 pub fn quix() {}

docs/reference/src/code/language/program-types/libraries/internal/my_library/src/lib.sw

@@ -1,6 +1,6 @@
-library lib;
+library;
 
-dep my_library;
+mod my_library;
 
 use my_library::bar;
 

docs/reference/src/code/language/program-types/libraries/internal/my_library/src/my_library.sw

@@ -1,6 +1,6 @@
 // ANCHOR: library
 // ANCHOR: module
-library my_library;
+library;
 // ANCHOR_END: module
 
 // Cannot import because the `pub` keyword is missing

docs/reference/src/code/language/style-guide/annotations/src/lib.sw

@@ -1,4 +1,4 @@
-library annotations;
+library;
 
 // ANCHOR: type_annotation
 fn execute() {

docs/reference/src/code/language/style-guide/enums/src/lib.sw

@@ -1,4 +1,4 @@
-library enums;
+library;
 
 pub enum Error {
     StateError: StateError,

docs/reference/src/code/language/style-guide/getters/src/lib.sw

@@ -1,4 +1,4 @@
-library getters;
+library;
 
 // ANCHOR: avoid
 fn get_maximum_deposit() -> u64 {

docs/reference/src/code/language/style-guide/letter_casing/src/lib.sw

@@ -1,5 +1,5 @@
 // ANCHOR: module
-library letter_casing;
+library;
 // ANCHOR_END: module
 // ANCHOR: const
 const MAXIMUM_DEPOSIT = 10;

docs/reference/src/code/language/style-guide/struct_shorthand/src/lib.sw

@@ -1,4 +1,4 @@
-library struct_shorthand;
+library;
 
 // ANCHOR: struct_shorthand_definition
 struct Structure {

docs/reference/src/code/language/variables/src/lib.sw

@@ -1,4 +1,4 @@
-library variables;
+library;
 
 fn mutable() {
     // ANCHOR: mutable

docs/reference/src/code/misc/advanced-concepts/enums/src/lib.sw

@@ -1,4 +1,4 @@
-library enums;
+library;
 
 // ANCHOR: u64_example
 pub enum T {

docs/reference/src/code/misc/known-issues/arrays/src/lib.sw

@@ -1,4 +1,4 @@
-library arrays;
+library;
 
 // ANCHOR: syntax
 fn syntax() {

docs/reference/src/code/misc/known-issues/strings/src/lib.sw

@@ -1,4 +1,4 @@
-library strings;
+library;
 
 fn single_quotes() {
     // ANCHOR: single_quotes

docs/reference/src/code/operations/assertions/src/lib.sw

@@ -1,6 +1,6 @@
-library assertions;
+library;
 
-dep req;
+mod req;
 
 // ANCHOR: assert
 fn subtract(a: u64, b: u64) -> u64 {

docs/reference/src/code/operations/assertions/src/req.sw

@@ -1,4 +1,4 @@
-library req;
+library;
 
 // ANCHOR: require
 fn subtract(a: u64, b: u64) -> u64 {

docs/reference/src/code/operations/asset_operations/src/lib.sw

@@ -1,4 +1,4 @@
-library asset_operations;
+library;
 
 // ANCHOR: mint_import
 use std::token::mint;

docs/reference/src/code/operations/call_data/src/lib.sw

@@ -1,4 +1,4 @@
-library call_data;
+library;
 
 // ANCHOR: import_sender
 use std::auth::msg_sender;

docs/reference/src/code/operations/contract_calling/interface/src/lib.sw

@@ -1,4 +1,4 @@
-library interface;
+library;
 
 abi Vault {
     fn deposit();

docs/reference/src/code/operations/hashing/src/lib.sw

@@ -1,4 +1,4 @@
-library hashing;
+library;
 
 // ANCHOR: import_sha256
 use std::hash::sha256;

docs/reference/src/code/operations/logging/src/lib.sw

@@ -1,4 +1,4 @@
-library logging;
+library;
 
 // ANCHOR: logging
 fn log_data(number: u64) {

docs/reference/src/code/operations/namespace/src/lib.sw

@@ -1,4 +1,4 @@
-library namespace;
+library;
 
 // ANCHOR: address
 pub struct Address {

docs/reference/src/documentation/language/program-types/libraries/index.md

@@ -4,7 +4,7 @@ A library is used to contain code that performs common operations in order to pr
 
 ## Definition
 
-Libraries are defined using the `library` keyword at the beginning of a file followed by a name so that they can be identified and imported.
+Libraries are defined using the `library` keyword at the beginning of a file.
 
 ```sway
 {{#include ../../../../code/language/program-types/libraries/internal/my_library/src/my_library.sw:module}}

docs/reference/src/documentation/language/program-types/libraries/internal.md

@@ -14,7 +14,7 @@ $ tree
 
 To be able to use our library `my_library.sw` in `lib.sw` there are two steps to take:
 
-1. Bring our library into scope by using the `dep` keyword followed by the library name
+1. Bring our library into scope by using the `mod` keyword followed by the library name
 2. Use the `use` keyword to selectively import various items from the library
 
 ```sway

examples/cei_analysis/src/main.sw

@@ -1,6 +1,6 @@
 contract;
 
-dep other_contract;
+mod other_contract;
 
 use other_contract::*;
 

examples/cei_analysis/src/other_contract.sw

@@ -1,4 +1,4 @@
-library other_contract;
+library;
 
 abi OtherContract {
     #[payable]

examples/enums/src/basic_enum.sw

@@ -1,4 +1,4 @@
-library basic_enum;
+library;
 
 // Declare the enum
 enum Color {