Pause the AllSetActivity background animation more reliably.

- Pause the animation when the alpha <= 0.1f, rather than 0f
- Pause the animation when the AllSetActivity pauses
- Do not vibrate if the AllSetActivity is not resumed

Bug: 236924895
Test: manually launched AllSetActivity and swiped up at various speeds
Change-Id: I1019f680730cfc72e9ad305d7ae09cff8a1637be
(cherry picked from commit 5f6b07d3)