Query code actions and hovers from all related local language servers (#9943)

<img width="1122" alt="Screenshot 2024-03-28 at 21 51 18"
src="https://github.com/zed-industries/zed/assets/2690773/37ef7202-f10f-462f-a2fa-044b2d806191">


Part of https://github.com/zed-industries/zed/issues/7947 and
https://github.com/zed-industries/zed/issues/9912 that adds makes Zed
query all related language servers instead of the primary one.

Collab clients are still querying the primary one only, but this is
quite hard to solve, https://github.com/zed-industries/zed/pull/8634
drafts a part of it.
The local part is useful per se, as many people use Zed & Tailwind but
do not use collab features.

Unfortunately, eslint still returns empty actions list when queried, but
querying actions for all related language servers looks reasonable and
rare enough to be dangerous.

Release Notes:

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

crates/copilot/src/copilot.rs

@@ -376,6 +376,7 @@ impl Copilot {
         use node_runtime::FakeNodeRuntime;
 
         let (server, fake_server) = FakeLanguageServer::new(
+            LanguageServerId(0),
             LanguageServerBinary {
                 path: "path/to/copilot".into(),
                 arguments: vec![],