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/vim/src/command.rs

@@ -490,9 +490,7 @@ mod test {
 
         assert_eq!(fs.load(&path).await.unwrap(), "@\n");
 
-        fs.as_fake()
-            .write_file_internal(path, "oops\n".to_string())
-            .unwrap();
+        fs.as_fake().insert_file(path, b"oops\n".to_vec()).await;
 
         // conflict!
         cx.simulate_keystrokes(["i", "@", "escape"]);