Revert "WM: Cleanup TestAppWindowToken code and promote ZOrderingTests to non-flaky"

This reverts commit 469dcbf77b3bd41f1e393f62322178bdae1140ba.

Reason for revert: ZOrderingTests are still flaky in postsubmit (go/wm-tests)

Change-Id: I30c8ed06986da7327324e1db749f79c7a7eb4da8
6 files changed