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/project/src/yarn.rs

@@ -91,9 +91,9 @@ impl YarnPathStore {
         };
         if let Some(zip_file) = zip_path(&path) {
             let zip_file: Arc<Path> = Arc::from(zip_file);
-            cx.spawn(|this, mut cx| async move {
+            cx.spawn(async move |this, cx| {
                 let dir = this
-                    .update(&mut cx, |this, _| {
+                    .update(cx, |this, _| {
                         this.temp_dirs
                             .get(&zip_file)
                             .map(|temp| temp.path().to_owned())
@@ -102,10 +102,10 @@ impl YarnPathStore {
                 let zip_root = if let Some(dir) = dir {
                     dir
                 } else {
-                    let fs = this.update(&mut cx, |this, _| this.fs.clone()).ok()?;
+                    let fs = this.update(cx, |this, _| this.fs.clone()).ok()?;
                     let tempdir = dump_zip(zip_file.clone(), fs).await.log_err()?;
                     let new_path = tempdir.path().to_owned();
-                    this.update(&mut cx, |this, _| {
+                    this.update(cx, |this, _| {
                         this.temp_dirs.insert(zip_file.clone(), tempdir);
                     })
                     .ok()?;