RESTRICT AUTOMERGE Fix alternateBouncer => primaryBouncer flicker

This involves a series of fixes:
1. Don't update the scrim state between
hiding the alternate bouncer and showing the
primary bouncer. This can cause the scrim state to
transition to the UNLOCKED scrim between AUTH_SCRIMMED_SHADE
and BOUNCER_SCRIMMED.
2. Handle the AlternateBouncer touch on action up. The AlternateBouncer
intercepts all touch events when its visible. We don't want to
prematurely stop intercepting the touch after the initial down event,
or else the touch can be sent to its parent view (notification
shade) while the alternate bouncer is going away which can cause
flicker. Therefore, don't trigger the transition to the primary bouncer
until action UP.

Test: atest StatusBarKeyguardViewManagerTest
Test: bring up the altnerate bouncer over the shade
over an occluding activity, and then tap anywhere
to bring up the primary bouncer. Observe there's no flicker.
Bug: 272350664

Change-Id: I1c68ceb9bb77b0b664ca351af1a897b835e80367