Refactor to use SharedString in more places (#23813)

Splitting this off from
https://github.com/zed-industries/zed/pull/23808, per @maxdeviant's
suggestion!

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/repl/src/repl_editor.rs

@@ -454,7 +454,7 @@ fn markdown_code_blocks(buffer: &BufferSnapshot, range: Range<Point>) -> Vec<Ran
 }
 
 fn language_supported(language: &Arc<Language>) -> bool {
-    match language.name().0.as_ref() {
+    match language.name().as_ref() {
         "TypeScript" | "Python" => true,
         _ => false,
     }