cx.background_executor().spawn(...) -> cx.background_spawn(...) (#25103)

Done automatically with

> ast-grep -p '$A.background_executor().spawn($B)' -r
'$A.background_spawn($B)' --update-all --globs "\!crates/gpui"

Followed by:

* `cargo fmt`
* Unexpected need to remove some trailing whitespace.
* Manually adding imports of `gpui::{AppContext as _}` which provides
`background_spawn`
* Added `AppContext as _` to existing use of `AppContext`

Release Notes:

- N/A

crates/remote_server/src/unix.rs

@@ -311,7 +311,7 @@ fn start_server(
             let mut output_buffer = Vec::new();
 
             let (mut stdin_msg_tx, mut stdin_msg_rx) = mpsc::unbounded::<Envelope>();
-            cx.background_executor().spawn(async move {
+            cx.background_spawn(async move {
                 while let Ok(msg) = read_message(&mut stdin_stream, &mut input_buffer).await {
                     if let Err(_) = stdin_msg_tx.send(msg).await {
                         break;
@@ -487,8 +487,7 @@ pub fn execute_run(
 
         handle_panic_requests(&project, &session);
 
-        cx.background_executor()
-            .spawn(async move { cleanup_old_binaries() })
+        cx.background_spawn(async move { cleanup_old_binaries() })
             .detach();
 
         mem::forget(project);