[flexiglass] on showPrimaryBouncer, change to bouncer scene

Calls to showPrimaryBouncer occur when SysUI specifically
wants to show the primary bouncer and NOT the alternate bouncer.
An example of this is when there's a tap or swipe gesture
on the alternate bouncer, the primary bouncer should show.

Bug: 353955910
Flag: com.android.systemui.scene_container
Test: atest StatusBarKeyguardViewManagerTest
Change-Id: I36700ed58f5ce83837f5ae98ad5d8583d6159acc