Fix blank Bubbles related to unfold transition

Clean up a pending unfold transition from TaskViewTransitions when
it is consumed by a different handler.

Also only notify bubbles and queue the unfold transition when bubbles
are expanded.

Bug: 418131777
Flag: com.android.wm.shell.enable_bubble_bar
Test: atest BubbleTransitionsTest
Test: manual
       - expand floating bubble on a foldable
       - attach a magnetic charger
       - expand bubbles and verify expanded view is displayed
Change-Id: I6ee14b8c7c29474905335191527b9acd00ec4567