send request immediately to handler

The following methods are updated in this cl:
- startPointingUI
- removeListenerForPointingUI

Bug: 410309100
Test: atest PointingAppController
Flag: com.android.internal.telephony.flags.satellite_improve_multi_thread_design
Change-Id: Icec9abb6550b17d75f98d6f7b318acc322a59944