Make GitRepository::status async and remove cx parameter (#27514)

This lays the groundwork for using `status` as part of the new agent
panel.

Release Notes:

- N/A

crates/extension_host/src/extension_store_test.rs

@@ -477,7 +477,7 @@ async fn test_extension_store_with_test_extension(cx: &mut TestAppContext) {
     let test_extension_id = "test-extension";
     let test_extension_dir = root_dir.join("extensions").join(test_extension_id);
 
-    let fs = Arc::new(RealFs::default());
+    let fs = Arc::new(RealFs::new(None, cx.executor()));
     let extensions_dir = TempTree::new(json!({
         "installed": {},
         "work": {}