Skip repositioning home stack for recents animation if already visible

- When there is a translucent activity, the home stack was incorrectly
  being respositioned to the back before being moved to be behind the next
  visible stack.

Bug: 72946250
Test: atest ActivityStackTests
Change-Id: I87188cb0d6e0ee3de247fa812e151ea62ae0cdf7
2 files changed