Fix a bug where bubbles intercepted swipe gestures from fold->unfold

We need to tell stackview to stop monitoring the gesture when we
switch between modes -- do this when the view gets detached from
the window since that ensures it's always removed.

Flag: EXEMPT safe bugfix
Test: atest BubbleStackViewTest
Bug: 376529330
Change-Id: I8972f77ae9693af61fe13bffdc70cb9454e45cea