Fix jank in CUJ_NOTIFICATION_HEADS_UP_APPEAR

Use Choreographer to delay animation and mitigate jank in
J<NOTIFICATION_HEADS_UP_APPEAR>

Test: 1) setprop persist.debug.animator.trace_fraction true &&
      device_config put interaction_jank_monitor enabled true.
      2) Capture perfetto trace while posting test HUN. 3) Inspect the
      trace; verify that sysui's frames during the
      J<NOTIFICATION_HEADS_UP_APPEAR> CUJ are not in high latency state
Bug: 262705829
Change-Id: I34df2978310a27859725ede28dd556c35d4bd785