[flexiglass] Refactor scene switching logic to selectively hide overlays

When unlocking from the bouncer, if the shade is meant to stay open
(leaveOpenOnKeyguardHide is true), we should only dismiss the bouncer
and not all overlays. The previous logic always hid all overlays,
causing the attached bug (where the QS shade would be closed after
authenticating).

This change makes the device unlock logic only hide the shade or QS overlays if leaveOpen is false.

Fix: 434645851
Test: Manually verified by unlocking the device by tapping on the edit
button in the QS shade overlay or from a notification in the
notification shade overlay and confirming the shade remains visible
after unlocking
Flag: com.android.systemui.scene_container

Change-Id: Icede3c05d21fff5337890a52e54c2d003869c51a