Do not wait for window with alpha=0

It can be considered as invisible.

The legacy transition also uses similar condition in
RrecentsAnimationController#isInterestingForAllDrawn.

Bug: 276717081
Test: Enable -1 screen and swipe up from app, isSyncFinished()
      can return true directly even if the drawn state is pending.

Change-Id: I711e35220e4386b4ad1a84a0f69719c9aa4e5a52