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/outline_panel/src/outline_panel.rs

@@ -171,7 +171,7 @@ impl SearchState {
                 })
                 .collect(),
             highlight_search_match_tx,
-            _search_match_highlighter: cx.background_executor().spawn(async move {
+            _search_match_highlighter: cx.background_spawn(async move {
                 while let Ok(highlight_arguments) = highlight_search_match_rx.recv().await {
                     let needs_init = highlight_arguments.search_data.get().is_none();
                     let search_data = highlight_arguments.search_data.get_or_init(|| {
@@ -681,8 +681,7 @@ impl OutlinePanel {
         mut cx: AsyncWindowContext,
     ) -> anyhow::Result<Entity<Self>> {
         let serialized_panel = cx
-            .background_executor()
-            .spawn(async move { KEY_VALUE_STORE.read_kvp(OUTLINE_PANEL_KEY) })
+            .background_spawn(async move { KEY_VALUE_STORE.read_kvp(OUTLINE_PANEL_KEY) })
             .await
             .context("loading outline panel")
             .log_err()
@@ -849,7 +848,7 @@ impl OutlinePanel {
     fn serialize(&mut self, cx: &mut Context<Self>) {
         let width = self.width;
         let active = Some(self.active);
-        self.pending_serialization = cx.background_executor().spawn(
+        self.pending_serialization = cx.background_spawn(
             async move {
                 KEY_VALUE_STORE
                     .write_kvp(
@@ -2631,8 +2630,7 @@ impl OutlinePanel {
                 new_depth_map,
                 new_children_count,
             )) = cx
-                .background_executor()
-                .spawn(async move {
+                .background_spawn(async move {
                     let mut processed_external_buffers = HashSet::default();
                     let mut new_worktree_entries =
                         BTreeMap::<WorktreeId, HashMap<ProjectEntryId, GitEntry>>::default();
@@ -3224,8 +3222,7 @@ impl OutlinePanel {
                     (buffer_id, excerpt_id),
                     cx.spawn_in(window, |outline_panel, mut cx| async move {
                         let fetched_outlines = cx
-                            .background_executor()
-                            .spawn(async move {
+                            .background_spawn(async move {
                                 buffer_snapshot
                                     .outline_items_containing(
                                         excerpt_range.context,