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/copilot/src/sign_in.rs

@@ -37,11 +37,11 @@ pub fn initiate_sign_in(window: &mut Window, cx: &mut App) {
             });
 
             let workspace = workspace.downgrade();
-            cx.spawn(|mut cx| async move {
+            cx.spawn(async move |cx| {
                 task.await;
                 if let Some(copilot) = cx.update(|cx| Copilot::global(cx)).ok().flatten() {
                     workspace
-                        .update(&mut cx, |workspace, cx| match copilot.read(cx).status() {
+                        .update(cx, |workspace, cx| match copilot.read(cx).status() {
                             Status::Authorized => workspace.show_toast(
                                 Toast::new(
                                     NotificationId::unique::<CopilotStartingToast>(),