lsp: Do not drop lsp buffer handle from editor when a language change leads to buffer having a legit language (#44469)

Fixes a bug that led to us unnecessarily restarting a language server
when we were looking at a single file of a given language.

Release Notes:

- Fixed a bug that led to Zed sometimes starting an excessive amount of
language servers

crates/project/src/buffer_store.rs

@@ -1141,7 +1141,7 @@ impl BufferStore {
                     })
                     .log_err();
             }
-            BufferEvent::LanguageChanged => {}
+            BufferEvent::LanguageChanged(_) => {}
             _ => {}
         }
     }

crates/project/src/git_store.rs

@@ -1451,7 +1451,7 @@ impl GitStore {
         match event {
             BufferStoreEvent::BufferAdded(buffer) => {
                 cx.subscribe(buffer, |this, buffer, event, cx| {
-                    if let BufferEvent::LanguageChanged = event {
+                    if let BufferEvent::LanguageChanged(_) = event {
                         let buffer_id = buffer.read(cx).remote_id();
                         if let Some(diff_state) = this.diffs.get(&buffer_id) {
                             diff_state.update(cx, |diff_state, cx| {

crates/project/src/lsp_store.rs

@@ -219,7 +219,7 @@ struct UnifiedLanguageServer {
     project_roots: HashSet<Arc<RelPath>>,
 }
 
-#[derive(Clone, Hash, PartialEq, Eq)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
 struct LanguageServerSeed {
     worktree_id: WorktreeId,
     name: LanguageServerName,