Byte conversion for primitives (FuelLabs#4630)

## Description
closes FuelLabs#4626 

## Checklist

- [x] I have linked to any relevant issues.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] 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.
- [ ] 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.

---------

Co-authored-by: Marcos Henrich <[email protected]>

sway-lib-core/src/lib.sw

@@ -4,6 +4,7 @@ pub mod primitives;
 pub mod raw_ptr;
 pub mod raw_slice;
 pub mod ops;
+pub mod primitive_conversions;
 pub mod never;
 pub mod r#storage;
 pub mod prelude;