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/languages/src/json.rs

@@ -269,7 +269,15 @@ impl JsonLspAdapter {
             .await;
 
         let config = cx.update(|cx| {
-            Self::get_workspace_config(self.languages.language_names().clone(), adapter_schemas, cx)
+            Self::get_workspace_config(
+                self.languages
+                    .language_names()
+                    .into_iter()
+                    .map(|name| name.to_string())
+                    .collect(),
+                adapter_schemas,
+                cx,
+            )
         })?;
         writer.replace(config.clone());
         return Ok(config);