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/project/src/lsp_command/signature_help.rs

@@ -86,7 +86,7 @@ impl SignatureHelp {
         } else {
             let markdown = markdown.join(str_for_join);
             let language_name = language
-                .map(|n| n.name().0.to_lowercase())
+                .map(|n| n.name().as_ref().to_lowercase())
                 .unwrap_or_default();
 
             let markdown = if function_options_count >= 2 {

crates/project/src/project.rs

@@ -2579,7 +2579,7 @@ impl Project {
         language_name: LanguageName,
     ) -> Option<SharedString> {
         languages
-            .language_for_name(&language_name.0)
+            .language_for_name(language_name.as_ref())
             .await
             .ok()?
             .toolchain_lister()

crates/project/src/task_inventory.rs

@@ -10,7 +10,7 @@ use std::{
 
 use anyhow::{Context as _, Result};
 use collections::{HashMap, HashSet, VecDeque};
-use gpui::{App, AppContext as _, Entity, Task};
+use gpui::{App, AppContext as _, Entity, SharedString, Task};
 use itertools::Itertools;
 use language::{ContextProvider, File, Language, LanguageToolchainStore, Location};
 use settings::{parse_json_with_comments, SettingsLocation};
@@ -53,7 +53,7 @@ pub enum TaskSourceKind {
         abs_path: PathBuf,
     },
     /// Languages-specific tasks coming from extensions.
-    Language { name: Arc<str> },
+    Language { name: SharedString },
 }
 
 impl TaskSourceKind {
@@ -91,7 +91,7 @@ impl Inventory {
         cx: &App,
     ) -> Vec<(TaskSourceKind, TaskTemplate)> {
         let task_source_kind = language.as_ref().map(|language| TaskSourceKind::Language {
-            name: language.name().0,
+            name: language.name().into(),
         });
         let global_tasks = self.global_templates_from_settings();
         let language_tasks = language
@@ -124,7 +124,7 @@ impl Inventory {
             .as_ref()
             .and_then(|location| location.buffer.read(cx).language_at(location.range.start));
         let task_source_kind = language.as_ref().map(|language| TaskSourceKind::Language {
-            name: language.name().0,
+            name: language.name().into(),
         });
         let file = location
             .as_ref()

crates/project/src/toolchain_store.rs

@@ -316,7 +316,10 @@ impl LocalToolchainStore {
 
             cx.background_executor()
                 .spawn(async move {
-                    let language = registry.language_for_name(&language_name.0).await.ok()?;
+                    let language = registry
+                        .language_for_name(language_name.as_ref())
+                        .await
+                        .ok()?;
                     let toolchains = language.toolchain_lister()?;
                     Some(toolchains.list(root.to_path_buf(), project_env).await)
                 })