Add initial support for defining language server adapters in WebAssembly-based extensions (#8645)

This PR adds **internal** ability to run arbitrary language servers via
WebAssembly extensions. The functionality isn't exposed yet - we're just
landing this in this early state because there have been a lot of
changes to the `LspAdapter` trait, and other language server logic.

## Next steps

* Currently, wasm extensions can only define how to *install* and run a
language server, they can't yet implement the other LSP adapter methods,
such as formatting completion labels and workspace symbols.
* We don't have an automatic way to install or develop these types of
extensions
* We don't have a way to package these types of extensions in our
extensions repo, to make them available via our extensions API.
* The Rust extension API crate, `zed-extension-api` has not yet been
published to crates.io, because we still consider the API a work in
progress.

Release Notes:

- N/A

---------

Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Nathan <nathan@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/collab/src/tests.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use call::Room;
 use client::ChannelId;
 use gpui::{Model, TestAppContext};
@@ -15,6 +17,7 @@ mod random_project_collaboration_tests;
 mod randomized_test_helpers;
 mod test_server;
 
+use language::{tree_sitter_rust, Language, LanguageConfig, LanguageMatcher};
 pub use randomized_test_helpers::{
     run_randomized_test, save_randomized_test_plan, RandomizedTest, TestError, UserTestPlan,
 };
@@ -47,3 +50,17 @@ fn room_participants(room: &Model<Room>, cx: &mut TestAppContext) -> RoomPartici
 fn channel_id(room: &Model<Room>, cx: &mut TestAppContext) -> Option<ChannelId> {
     cx.read(|cx| room.read(cx).channel_id())
 }
+
+fn rust_lang() -> Arc<Language> {
+    Arc::new(Language::new(
+        LanguageConfig {
+            name: "Rust".into(),
+            matcher: LanguageMatcher {
+                path_suffixes: vec!["rs".to_string()],
+                ..Default::default()
+            },
+            ..Default::default()
+        },
+        Some(tree_sitter_rust::language()),
+    ))
+}