[Bubble] Fix flicker related to start animation moving view outside display

If the TaskView is moved outside the display bounds, the appBounds of
the Activity inside the Task window is cropped. This caused flicker
because the appBounds changed between the beginning and ending of the
animation, which triggered app relayout. This change moves the
starting position into the animator instead of moving the view before
the animation to prevent the flicker.

Bug: 424205239
Test: Manual
Flag: EXEMPT bugfix
Change-Id: I42338b5a29e817cdba1924a6290be0b00cb19ccf