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/feedback/src/system_specs.rs

@@ -1,5 +1,5 @@
 use client::telemetry;
-use gpui::{App, Task, Window};
+use gpui::{App, AppContext as _, Task, Window};
 use human_bytes::human_bytes;
 use release_channel::{AppCommitSha, AppVersion, ReleaseChannel};
 use serde::Serialize;
@@ -44,7 +44,7 @@ impl SystemSpecs {
             None
         };
 
-        cx.background_executor().spawn(async move {
+        cx.background_spawn(async move {
             let os_version = telemetry::os_version();
             SystemSpecs {
                 app_version,