debugger_ui: Preview thread state when using the dropdown (#28778)

This PR changes the thread list dropdown menu in the debugger UI to
eagerly preview the state of a thread when selecting it, instead of
waiting until confirming the selection.

Release Notes:

- N/A

crates/debugger_ui/src/session/running.rs

@@ -768,7 +768,7 @@ impl RunningState {
         DropdownMenu::new(
             ("thread-list", self.session_id.0),
             selected_thread_name,
-            ContextMenu::build(window, cx, move |mut this, _, _| {
+            ContextMenu::build_eager(window, cx, move |mut this, _, _| {
                 for (thread, _) in threads {
                     let state = state.clone();
                     let thread_id = thread.id;