Add API to monitor selected satellite subscription changed event.

1. Added registerForSelectedNbIotSatelliteSubscriptionChanged/unregisterForSelectedNbIotSatelliteSubscriptionChanged into SatelliteManager

Bug: 378557737
Change-Id: I915fc00f5e9c54ceb1e3a9b3bee0b5f8036b6ea0
Test: atest SatelliteManagerTest, SatelliteManagerTestOnMockService
FLAG: com.android.internal.telephony.flags.carrier_roaming_nb_iot_ntn