Pass the Bubble to BBEV on init

We now pass the bubble to bubble bar expanded view when initializing
it. This is prework to transitioning a floating bubble to a bar
bubble.

Also cleanup some testing logic.

Bug: 392893178
Flag: com.android.wm.shell.enable_bubble_bar
Test: manual -- just make sure things still work
       - send some bubbles
       - remove bubbles
       - switch bubbles
Change-Id: I600d99458d594279b737bb25a5df8d3e7fd6729d