Make the compose bouncer run on a narrower scope.

Summary of changes:
 1. Makes sure the mBouncerParentView is initialized and wired up before collecting flows that update the view state
 2. Bouncer parent view is now removed when any PRIMARY_BOUNCER -> * transition finishes
 3. Bouncer parent view is now added when any * -> PRIMARY_BOUNCER transition starts

Fixes: 361793133
Test: Tested all primary bouncer CUJs using the compose bouncer.
Flag: com.android.systemui.compose_bouncer
Change-Id: I69c3b19a4f27b4f78b100631950a78bcbdf08e93