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/project_symbols/src/project_symbols.rs

@@ -292,7 +292,7 @@ mod tests {
 
         let _buffer = project
             .update(cx, |project, cx| {
-                project.open_local_buffer("/dir/test.rs", cx)
+                project.open_local_buffer_with_lsp("/dir/test.rs", cx)
             })
             .await
             .unwrap();