[Fold to AOD] Respect screen off animation status in navbar when keyguard is showing

Forces navigation bar to hide when fold to AOD
animation is playing when keyguard is already displayed.
This could happen when device is unfolded and
already showing the lockscreen and we start folding it.

Also adds a functional test that checks this behavior.

Bug: 202844967
Test: phone is locked and showing keyguard, fold
 => check that navbar is not visible
Test: atest android.platform.test.scenario.sysui.foldable.FoldToAod
Change-Id: Ibef318a723b73e9c5a5c322380fff84ecbb3533e