Flexiglass: visual stability on lockscreen

Pre-Flexiglass, the notion of "panel expanded" included when the stack
was visible on the lockscreen but the shade wasn't actually expanded.

Under Flexiglass, "panel expanded" means, literally, that the panel is
expanded, and is therefore *false* on the lockscreen.

Unfortunately, VisualStabilityCoordinator was relying on that as a
signal for when to enforce stability. Therefore, fix it to listen for
the lockscreen scene (using KeyguardTransitionInteractor) as well.

Bug: 332558345
Test: manual: turn on Flexi, turn on VisualStability logs, turn screen off and on
Flag: com.android.systemui.scene_container
Change-Id: I1d38dd580a95006159380e7ebb4b1876b5c27805