Add CTS test for onCarrierRoamingNtnSignalStrengthChanged callback.

Bug: 350396906
Test: atest TelephonyRegistryManagerTest, TelephonyCallbackTest,
Test: Manually tested SMS/MMS/CALLS/DATA
Flag: com.android.internal.telephony.flags.carrier_roaming_nb_iot_ntn
Change-Id: I481a70a8d9ea0b13988deae7f77e05362e55dab3
2 files changed