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/multi_buffer/src/multi_buffer.rs

@@ -129,7 +129,7 @@ pub enum Event {
         transaction_id: TransactionId,
     },
     Reloaded,
-    LanguageChanged(BufferId),
+    LanguageChanged(BufferId, bool),
     Reparsed(BufferId),
     Saved,
     FileHandleChanged,
@@ -2294,7 +2294,9 @@ impl MultiBuffer {
             BufferEvent::Saved => Event::Saved,
             BufferEvent::FileHandleChanged => Event::FileHandleChanged,
             BufferEvent::Reloaded => Event::Reloaded,
-            BufferEvent::LanguageChanged => Event::LanguageChanged(buffer_id),
+            BufferEvent::LanguageChanged(has_language) => {
+                Event::LanguageChanged(buffer_id, *has_language)
+            }
             BufferEvent::Reparsed => Event::Reparsed(buffer_id),
             BufferEvent::DiagnosticsUpdated => Event::DiagnosticsUpdated,
             BufferEvent::CapabilityChanged => {