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/vim/src/state.rs

@@ -288,8 +288,8 @@ impl MarksState {
     }
 
     fn load(&mut self, cx: &mut Context<Self>) {
-        cx.spawn(|this, mut cx| async move {
-            let Some(workspace_id) = this.update(&mut cx, |this, cx| this.workspace_id(cx))? else {
+        cx.spawn(async move |this, cx| {
+            let Some(workspace_id) = this.update(cx, |this, cx| this.workspace_id(cx))? else {
                 return Ok(());
             };
             let (marks, paths) = cx
@@ -299,7 +299,7 @@ impl MarksState {
                     anyhow::Ok((marks, paths))
                 })
                 .await?;
-            this.update(&mut cx, |this, cx| this.loaded(marks, paths, cx))
+            this.update(cx, |this, cx| this.loaded(marks, paths, cx))
         })
         .detach_and_log_err(cx);
     }