Fix issues where the task was still touchable in overview

- Reparent above the top window as an activity can have multiple windows
- Fix ordering when reparenting tasks into the temporary split container
  to match the previous ordering since the input consumer is layered
  above the top window

Fixes: 197571005
Fixes: 195958376
Test: Launch maps > share place > enter overview
      Enable stage split > split > enter overview
Change-Id: I84899e71f079f001eef737217897642460f5832b