Corrects animation for moving ActivityEmbeddings

Previously, DesktopModeMoveToDisplayTransitionHandler applied animation
to a single TransitionInfo.Change. This was inadequate for
TransitionInfo moving a task with ActivityEmbedding, as it includes
three TransitionInfo.Change objects: one for each embedded activity and
one for the parent container. To fix the animation:

- Applies animation to all TransitionInfo.Change objects that involve
  moving to another display.

- Sets the relative position of the leash surface instead of the
  absolute position. This ensures the leash surface of embedded
  activities, parented to the container task, is placed correctly.

Bug: 376355478
Test: DesktopModeMoveToDisplayTransitionHandlerTest
Flag: com.android.window.flags.enable_move_to_next_display_shortcut
Change-Id: I3b6035c4aed42977a29defc4c9d23adaacf6d90a