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/src/buffer_store.rs

@@ -1,4 +1,5 @@
 use crate::{
+    lsp_store::OpenLspBufferHandle,
     search::SearchQuery,
     worktree_store::{WorktreeStore, WorktreeStoreEvent},
     ProjectItem as _, ProjectPath,
@@ -47,6 +48,7 @@ pub struct BufferStore {
 struct SharedBuffer {
     buffer: Model<Buffer>,
     unstaged_changes: Option<Model<BufferChangeSet>>,
+    lsp_handle: Option<OpenLspBufferHandle>,
 }
 
 #[derive(Debug)]
@@ -1571,6 +1573,21 @@ impl BufferStore {
         })?
     }
 
+    pub fn register_shared_lsp_handle(
+        &mut self,
+        peer_id: proto::PeerId,
+        buffer_id: BufferId,
+        handle: OpenLspBufferHandle,
+    ) {
+        if let Some(shared_buffers) = self.shared_buffers.get_mut(&peer_id) {
+            if let Some(buffer) = shared_buffers.get_mut(&buffer_id) {
+                buffer.lsp_handle = Some(handle);
+                return;
+            }
+        }
+        debug_panic!("tried to register shared lsp handle, but buffer was not shared")
+    }
+
     pub fn handle_synchronize_buffers(
         &mut self,
         envelope: TypedEnvelope<proto::SynchronizeBuffers>,
@@ -1597,6 +1614,7 @@ impl BufferStore {
                     .or_insert_with(|| SharedBuffer {
                         buffer: buffer.clone(),
                         unstaged_changes: None,
+                        lsp_handle: None,
                     });
 
                 let buffer = buffer.read(cx);
@@ -2017,6 +2035,7 @@ impl BufferStore {
             SharedBuffer {
                 buffer: buffer.clone(),
                 unstaged_changes: None,
+                lsp_handle: None,
             },
         );