Query code actions and hovers from all related local language servers (from remote clients) (#10111)

Supersedes https://github.com/zed-industries/zed/pull/8634
Fixes https://github.com/zed-industries/zed/issues/7947 by continuing
https://github.com/zed-industries/zed/pull/9943 with the remote part.

Now, clients are able to issue collab requests, that query all related
language servers, not only the primary one.
Such mode is enabled for GetHover and GetCodeActions LSP requests only.

Release Notes:

- Added Tailwind CSS hover popovers for Zed in multi player mode
([7947](https://github.com/zed-industries/zed/issues/7947))

crates/rpc/src/proto.rs

@@ -299,6 +299,8 @@ messages!(
     (SetRoomParticipantRole, Foreground),
     (BlameBuffer, Foreground),
     (BlameBufferResponse, Foreground),
+    (MultiLspQuery, Background),
+    (MultiLspQueryResponse, Background),
 );
 
 request_messages!(
@@ -390,6 +392,7 @@ request_messages!(
     (LspExtExpandMacro, LspExtExpandMacroResponse),
     (SetRoomParticipantRole, Ack),
     (BlameBuffer, BlameBufferResponse),
+    (MultiLspQuery, MultiLspQueryResponse),
 );
 
 entity_messages!(
@@ -418,6 +421,7 @@ entity_messages!(
     InlayHints,
     JoinProject,
     LeaveProject,
+    MultiLspQuery,
     OnTypeFormatting,
     OpenBufferById,
     OpenBufferByPath,