languages: Remove a eager conversion from LanguageName to String (#35667)

This PR changes the signature of `language_names` from

```rust
pub fn language_names(&self) -> Vec<String>
// Into
pub fn language_names(&self) -> Vec<LanguageName>
```

The function previously eagerly converted `LanguageName`'s to
`String`'s, which requires the reallocation of all of the elements. The
functions get called in many places in the code base, but only one of
which actually requires the conversion to a `String`. In one case it
would do a `SharedString` -> `String` -> `SharedString` conversion,
which is now totally bypassed.

Release Notes:

- N/A

crates/debugger_ui/src/new_process_modal.rs

@@ -1015,15 +1015,13 @@ impl DebugDelegate {
         let language_names = languages.language_names();
         let language = dap_registry
             .adapter_language(&scenario.adapter)
-            .map(|language| TaskSourceKind::Language {
-                name: language.into(),
-            });
+            .map(|language| TaskSourceKind::Language { name: language.0 });
 
         let language = language.or_else(|| {
             scenario.label.split_whitespace().find_map(|word| {
                 language_names
                     .iter()
-                    .find(|name| name.eq_ignore_ascii_case(word))
+                    .find(|name| name.as_ref().eq_ignore_ascii_case(word))
                     .map(|name| TaskSourceKind::Language {
                         name: name.to_owned().into(),
                     })