debugger: Remember pane layout from previous debugger session (#28692)

This PR makes a debugger's pane layout persistent across session's that
use the same debug adapter.

Release Notes:

- N/A

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Cole Miller <m@cole-miller.net>

crates/debugger_ui/src/tests/variable_list.rs

@@ -1538,6 +1538,8 @@ async fn test_variable_list_only_sends_requests_when_rendering(
         })
         .await;
 
+    cx.run_until_parked();
+
     let running_state = active_debug_session_panel(workspace, cx).update_in(cx, |item, _, _| {
         let state = item
             .mode()