FloatingWidgetView - avoid calling position callback when nothing changes.

Previously, the position changed callback for the transition animation
was called on every layout change, whether or not the position has changed.

Now only call the callback and the layout changes if the targets don't
match the current state.

Bug: 327696338
Flag: EXEMPT bug fix
Test: manual
Change-Id: I3007a1c8d0a869866c66eb14d75f5b48d977f863