Dequalify WindowContext and AsyncWindowContext identifiers (#22444)

This makes a WIP automated refactoring a bit easier to write

Release Notes:

- N/A

crates/editor/src/proposed_changes_editor.rs

@@ -288,7 +288,7 @@ impl EventEmitter<EditorEvent> for ProposedChangesEditor {}
 impl Item for ProposedChangesEditor {
     type Event = EditorEvent;
 
-    fn tab_icon(&self, _cx: &ui::WindowContext) -> Option<Icon> {
+    fn tab_icon(&self, _cx: &WindowContext) -> Option<Icon> {
         Some(Icon::new(IconName::Diff))
     }