Start to split out initialization and registration (#21787)

Still TODO:

* [x] Factor out `start_language_server` so we can call it on register
(instead of on detect language)
* [x] Only call register in singleton editors (or when
editing/go-to-definition etc. in a multibuffer?)
* [x] Refcount on register so we can unregister when no buffer remain
* [ ] (maybe) Stop language servers that are no longer needed after some
time

Release Notes:

- Fixed language servers starting when doing project search
- Fixed high CPU usage when ignoring warnings in the diagnostics view

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Cole <cole@zed.dev>

crates/remote_server/src/remote_editing_tests.rs

@@ -440,9 +440,9 @@ async fn test_remote_lsp(cx: &mut TestAppContext, server_cx: &mut TestAppContext
     // Wait for the settings to synchronize
     cx.run_until_parked();
 
-    let buffer = project
+    let (buffer, _handle) = project
         .update(cx, |project, cx| {
-            project.open_buffer((worktree_id, Path::new("src/lib.rs")), cx)
+            project.open_buffer_with_lsp((worktree_id, Path::new("src/lib.rs")), cx)
         })
         .await
         .unwrap();
@@ -616,9 +616,9 @@ async fn test_remote_cancel_language_server_work(
 
     cx.run_until_parked();
 
-    let buffer = project
+    let (buffer, _handle) = project
         .update(cx, |project, cx| {
-            project.open_buffer((worktree_id, Path::new("src/lib.rs")), cx)
+            project.open_buffer_with_lsp((worktree_id, Path::new("src/lib.rs")), cx)
         })
         .await
         .unwrap();