clutter/stage: Free pointer/touch info early during dispose

If we wait till finalize, dispose will destroy the actor hierarchy
and cause untimely repicks. Ensure to free the pointer/touch info
first, so the hooked signal callbacks are gone when destroying the
actors.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>

clutter/clutter/clutter-stage.c

@@ -1196,6 +1196,9 @@ clutter_stage_dispose (GObject *object)
   stage_manager = clutter_stage_manager_get_default ();
   _clutter_stage_manager_remove_stage (stage_manager, stage);
 
+  g_hash_table_remove_all (priv->pointer_devices);
+  g_hash_table_remove_all (priv->touch_sequences);
+
   G_OBJECT_CLASS (clutter_stage_parent_class)->dispose (object);
 }