Move AbstractFloatingView for stage split layering above all apps

- We don't need to worry about if it's in Overview. Only overview has task menus, so if there is no task menu, we place it at the top.

Fixes: 332465429
Test: Launch stage split using keyboard shortcuts with all apps open. Make sure it's above all apps.
Change-Id: Ic950d2897fe80ef407038dd840b86fc92d6d6287

quickstep/src/com/android/quickstep/views/FloatingTaskView.java

@@ -167,7 +167,7 @@ public class FloatingTaskView extends FrameLayout {
             // Add to top if not
             openTaskViewIndex = dragLayer.getChildCount();
         }
-        dragLayer.addView(floatingView, openTaskViewIndex - 1);
+        dragLayer.addView(floatingView, openTaskViewIndex);
         return floatingView;
     }