Only notify prepare-surface callback from window animator

Since the surface operations are centralized to window animator,
the operations that expect to run after transaction applied
should also be only executed by window animator.

Otherwise there could be a race:
 system-relayout: T1 shows the surface and sends surface to client.
 client: T2 applies hide.
 system-vsync: T1 is merged to T0, T0 is applied.
  -> expected hide but got overridden to show.

Bug: 318760302
Test: Disable animation and launch an app which requests to hide
      status bar. Keep switching between the app and home. Check
      that when the app is on top, the status bar is hidden.
Change-Id: Ic6f99be2907690fa955f6cfb424c4d0f68abf004