[flexiglass] Fixes issues that prevented falsing session from starting

See comments on the attached bug for details. TL;DR:
- FalsingCoreStartable which is responsible for initializing
  FalsingCollector doesn't initialize the real FalsingCollector when
  Flexiglass is on, leading to a disabled collector
- SceneContainerStartable's logic to report screen on/off was not
  running when AOD was available. There's no reason to condition that
  logic's running on the availability of AOD, the production logic
  doesn't do that

Fix: 365877972
Test: manually verified that, after a fresh device reboot, bringing up
the bouncer and tapping outside any PIN button a couple of times
correctly handles the false touch by force-navigating back to the
lockscreen scene
Test: unit tests updated
Flag: com.android.systemui.scene_container

Change-Id: Ib1d452c2ef0a42d49fdb5130a9da373697f8724e