upgrade to Rust v1.48.0 (pantsbuild#11210)

Upgrade to Rust v1.48.0.  https://blog.rust-lang.org/2020/11/19/Rust-1.48.html

- Disabled `clippy::manual_strip` which is triggered now in code generated by the macros in the `cpython` crate.
- Disabled `clippy::rc_buffer` in code that put a `Vec<PathStat>` in an `Arc`.

rust-toolchain

@@ -1 +1 @@
-1.47.0
+1.48.0

src/rust/engine/src/externs/fs.rs

@@ -29,6 +29,7 @@
 // File-specific allowances to silence internal warnings of `py_class!`.
 #![allow(
   unused_braces,
+  clippy::manual_strip,
   clippy::used_underscore_binding,
   clippy::transmute_ptr_to_ptr,
   clippy::zero_ptr

src/rust/engine/src/externs/interface.rs

@@ -29,6 +29,7 @@
 // File-specific allowances to silence internal warnings of `py_class!`.
 #![allow(
   unused_braces,
+  clippy::manual_strip,
   clippy::used_underscore_binding,
   clippy::transmute_ptr_to_ptr,
   clippy::zero_ptr

src/rust/engine/src/nodes.rs

@@ -1436,6 +1436,9 @@ pub enum NodeOutput {
   DirectoryListing(Arc<DirectoryListing>),
   LinkDest(LinkDest),
   ProcessResult(Box<ProcessResult>),
+  // Allow clippy::rc_buffer due to non-trivial issues that would arise in using the
+  // suggested Arc<[PathStat]> type. See https://github.com/rust-lang/rust-clippy/issues/6170
+  #[allow(clippy::rc_buffer)]
   Paths(Arc<Vec<PathStat>>),
   Value(Value),
 }

src/rust/engine/testutil/mock/src/action_cache.rs

@@ -18,9 +18,9 @@ clippy::unseparated_literal_suffix,
 #![allow(clippy::match_ref_pats)]
 // Subjective style.
 #![allow(
-clippy::len_without_is_empty,
-clippy::redundant_field_names,
-clippy::too_many_arguments
+  clippy::len_without_is_empty,
+  clippy::redundant_field_names,
+  clippy::too_many_arguments
 )]
 // Default isn't as big a deal as people seem to think it is.
 #![allow(clippy::new_without_default, clippy::new_ret_no_self)]

src/rust/engine/workunit_store/src/metrics.rs

@@ -18,9 +18,9 @@ clippy::unseparated_literal_suffix,
 #![allow(clippy::match_ref_pats)]
 // Subjective style.
 #![allow(
-clippy::len_without_is_empty,
-clippy::redundant_field_names,
-clippy::too_many_arguments
+  clippy::len_without_is_empty,
+  clippy::redundant_field_names,
+  clippy::too_many_arguments
 )]
 // Default isn't as big a deal as people seem to think it is.
 #![allow(clippy::new_without_default, clippy::new_ret_no_self)]