Add transition assertions for keyguard/aod API

Bug: 364930619
Bug: 396134691
Bug: 361438779
Test: atest 'DisplayContentTests#testKeyguardGoingAwayWhileAodShown'
Test: atest 'DisplayContentTests#testKeyguardGoingAwayCanceledWhileAodShown'
Flag: com.android.window.flags.ensure_keyguard_does_transition_starting
Flag: com.android.window.flags.aod_transition
Change-Id: I2f57ca5d10e49783bfd3568c0b99103dc47704df