Stop extensions' servers and message loops before removing their files (#34208)

Fixes an issue that caused Windows to fail when removing extension's
directories, as Zed had never stop any related processes.

Now:

* Zed shuts down and waits until the end when the language servers are
shut down

* Adds `impl Drop for WasmExtension` where does
`self.tx.close_channel();` to stop a receiver loop that holds the "lock"
on the extension's work dir.
The extension was dropped, but the channel was not closed for some
reason.

* Does more unregistration to ensure `Arc<WasmExtension>` with the `tx`
does not leak further

* Tidies up the related errors which had never reported a problematic
path before

Release Notes:

- N/A

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>
Co-authored-by: Smit <smit@zed.dev>

crates/remote_server/src/headless_project.rs

@@ -77,7 +77,6 @@ impl HeadlessProject {
         cx: &mut Context<Self>,
     ) -> Self {
         debug_adapter_extension::init(proxy.clone(), cx);
-        language_extension::init(proxy.clone(), languages.clone());
         languages::init(languages.clone(), node_runtime.clone(), cx);
 
         let worktree_store = cx.new(|cx| {
@@ -185,6 +184,11 @@ impl HeadlessProject {
         });
 
         cx.subscribe(&lsp_store, Self::on_lsp_store_event).detach();
+        language_extension::init(
+            language_extension::LspAccess::ViaLspStore(lsp_store.clone()),
+            proxy.clone(),
+            languages.clone(),
+        );
 
         cx.subscribe(
             &buffer_store,