Add onCarrierRoamingNtnSignalStrengthChanged callback.

Bug: 377030018
Test: atest SatelliteControllerTest, atest DefaultPhoneNotifierTest,
atest TelephonyRegistryTest
Test: Manually tested SMS/MMS/DATA/CALLS
FLAG: com.android.internal.telephony.flags.carrier_roaming_nb_iot_ntn

Change-Id: Ie3adda0fca0f7ecb6bfa676fceea7b8f083ce865