Attempt to show altBouncer before showing primary bouncer

This is in preparation for an implementation of
ActivityStarterInteralImpl#dismissKeyguardThenExecute
calling attemptDeviceEntry() which can show the alternateBouncer,
show the primaryBouncer, or immediately dismiss the device
depending on the state of the device.

Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT
Test: atest DeviceEntryInteractorTest
Bug: 308819693
Change-Id: I63f7982b552da7543b28772ebf21c9f5159f8cd1