Limit cases when we check if a bubble moves to split

BubblesTransitionObserver checks each transition to see if a bubbled
task is moving to split.
Add a check that we only check for open type transitions and if we have
bubbles.

Bug: 418591790
Test: atest WMShellUnitTests:BubblesTransitionObserverTest
Flag: com.android.wm.shell.enable_create_any_bubble
Change-Id: I93936ea74ae5650f0919094df3ee7924af3c0b2b