Allow to temporarily stop LSP servers (#28034)

Same as `editor::RestartLanguageServer`, now there's an
`editor::StopLanguageServer` action that stops all language servers,
related to the currently opened editor.

Opening another singleton editor with the same language or changing
selections in a multi buffer will bring the servers back up.

Release Notes:

- Added a way to temporarily stop LSP servers

---------

Co-authored-by: Michael Sloan <mgsloan@gmail.com>

crates/proto/src/proto.rs

@@ -400,6 +400,7 @@ messages!(
     (RespondToChannelInvite, Foreground),
     (RespondToContactRequest, Foreground),
     (RestartLanguageServers, Foreground),
+    (StopLanguageServers, Background),
     (RoomUpdated, Foreground),
     (SaveBuffer, Foreground),
     (SendChannelMessage, Background),
@@ -593,6 +594,7 @@ request_messages!(
     (RejoinRemoteProjects, RejoinRemoteProjectsResponse),
     (MultiLspQuery, MultiLspQueryResponse),
     (RestartLanguageServers, Ack),
+    (StopLanguageServers, Ack),
     (OpenContext, OpenContextResponse),
     (CreateContext, CreateContextResponse),
     (SynchronizeContexts, SynchronizeContextsResponse),
@@ -674,6 +676,7 @@ entity_messages!(
     LoadCommitDiff,
     MultiLspQuery,
     RestartLanguageServers,
+    StopLanguageServers,
     OnTypeFormatting,
     OpenNewBuffer,
     OpenBufferById,