Update nav and status bar visibility checks on flicker

Previously checked:
  - bar visible -> invisible -> visible again (rotation)
  - bar always visible (non-rotation)

However, these checks were unstable and the animation changed during the release, making the tests hard to maintain.

For now check only that the nav and status bar exist at the end of the transition

Bug: 189804667
Bug: 186115871
Test: atest FlickerTests WMShellFlickerTests
Change-Id: I5e34ae7e1af8bfcab56461617aaac9aa326e75b3