Move "async move" a few characters to the left in cx.spawn() (#26758)

This is the core change:
https://github.com/zed-industries/zed/pull/26758/files#diff-044302c0d57147af17e68a0009fee3e8dcdfb4f32c27a915e70cfa80e987f765R1052

TODO:
- [x] Use AsyncFn instead of Fn() -> Future in GPUI spawn methods
- [x] Implement it in the whole app
- [x] Implement it in the debugger 
- [x] Glance at the RPC crate, and see if those box future methods can
be switched over. Answer: It can't directly, as you can't make an
AsyncFn* into a trait object. There's ways around that, but they're all
more complex than just keeping the code as is.
- [ ] Fix platform specific code

Release Notes:

- N/A

crates/collab_ui/src/notifications/incoming_call_notification.rs

@@ -12,12 +12,12 @@ use workspace::AppState;
 pub fn init(app_state: &Arc<AppState>, cx: &mut App) {
     let app_state = Arc::downgrade(app_state);
     let mut incoming_call = ActiveCall::global(cx).read(cx).incoming();
-    cx.spawn(|mut cx| async move {
+    cx.spawn(async move |cx| {
         let mut notification_windows: Vec<WindowHandle<IncomingCallNotification>> = Vec::new();
         while let Some(incoming_call) = incoming_call.next().await {
             for window in notification_windows.drain(..) {
                 window
-                    .update(&mut cx, |_, window, _| {
+                    .update(cx, |_, window, _| {
                         window.remove_window();
                     })
                     .log_err();
@@ -75,7 +75,7 @@ impl IncomingCallNotificationState {
             let initial_project_id = self.call.initial_project.as_ref().map(|project| project.id);
             let app_state = self.app_state.clone();
             let cx: &mut App = cx;
-            cx.spawn(|cx| async move {
+            cx.spawn(async move |cx| {
                 join.await?;
                 if let Some(project_id) = initial_project_id {
                     cx.update(|cx| {