[flexiglass] Adds support freezeAndAnimateToCurrentState

This way, a half-way done transition can revert-animate to the previous scene even if the transition is still ongoing.

Bug: 396191914
Test: manually verified that pulling up the bouncer or pulling down the
shade, keeping the finger down, and pressing the power button correctly
moves back to the Lockscreen scene and puts it in AOD mode
Test: manually verified transitions into and out of AOD still works when
on the lockscreen scene
Flag: com.android.systemui.scene_container

Change-Id: I0d17373864e89d85b8661c37d95cb295f75fadb2