chore: Clippy fixes for 1.80 (#13987)

The biggest hurdle turned out to be use of `Arc<Language>` in maps, as
`clippy::mutable_key_type` started triggering on it (due to - I suppose
- internal mutability on `HighlightMap`?). I switched over to using
`LanguageId` as the key type in some of the callsites, as that's what
`Language` uses anyways for it's hash/eq, though I've still had to
suppress the lint outside of language crate.

/cc @maxdeviant , le clippy guru.

Release Notes:

- N/A

crates/project/src/project.rs

@@ -4106,6 +4106,7 @@ impl Project {
             return;
         }
 
+        #[allow(clippy::mutable_key_type)]
         let language_server_lookup_info: HashSet<(Model<Worktree>, Arc<Language>)> = buffers
             .into_iter()
             .filter_map(|buffer| {
@@ -11066,6 +11067,7 @@ async fn populate_labels_for_symbols(
     lsp_adapter: Option<Arc<CachedLspAdapter>>,
     output: &mut Vec<Symbol>,
 ) {
+    #[allow(clippy::mutable_key_type)]
     let mut symbols_by_language = HashMap::<Option<Arc<Language>>, Vec<CoreSymbol>>::default();
 
     let mut unknown_path = None;