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/command_palette/src/command_palette.rs

@@ -327,13 +327,13 @@ impl PickerDelegate for CommandPaletteDelegate {
         });
         self.updating_matches = Some((task, rx.clone()));
 
-        cx.spawn_in(window, move |picker, mut cx| async move {
+        cx.spawn_in(window, async move |picker, cx| {
             let Some((commands, matches)) = rx.recv().await else {
                 return;
             };
 
             picker
-                .update(&mut cx, |picker, cx| {
+                .update(cx, |picker, cx| {
                     picker
                         .delegate
                         .matches_updated(query, commands, matches, cx)