tests: Add test case for restoring focus after overview

This is a test case for
https://gitlab.gnome.org/GNOME/mutter/-/issues/2690.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3185>

src/tests/meson.build

@@ -696,6 +696,7 @@ stacking_tests = [
   'workspace-unmanaging-window',
   'click-to-focus-and-raise',
   'workspace-only-on-primary-focus',
+  'overview-focus',
 ]
 
 foreach stacking_test: stacking_tests

src/tests/stacking/overview-focus.metatest

@@ -0,0 +1,44 @@
+new_client w wayland
+
+create w/1
+show w/1
+wait
+assert_focused w/1
+hide w/1
+destroy w/1
+
+toggle_overview
+
+create w/1
+show w/1
+wait
+assert_focused none
+
+toggle_overview
+
+assert_focused w/1
+hide w/1
+destroy w/1
+
+
+new_client x x11
+
+create x/1
+show x/1
+wait
+assert_focused x/1
+hide x/1
+destroy x/1
+
+toggle_overview
+
+create x/1
+show x/1
+wait
+assert_focused none
+
+toggle_overview
+
+assert_focused x/1
+hide x/1
+destroy x/1