remove in-exact match for emergency numbers

-deprecates TelephonyManager#IsPotenTialEmergencyNumber
-deprecates PhoneNumberUtils#isPotentialEmergencyNumber
-removes hidden apis from PhoneNumberUtils with no usages
https://data.corp.google.com/sites/ezo8cfiu8snw/combined_api_checker/?f=signature:in:Landroid%2Ftelephony%2FPhoneNumberUtils;-%3EisPotentialEmergencyNumber(Ljava%2Flang%2FString;)Z,Landroid%2Ftelephony%2FPhoneNumberUtils;-%3EisPotentialEmergencyNumber(Ljava%2Flang%2FString;Ljava%2Flang%2FString;)Z,Landroid%2Ftelephony%2FPhoneNumberUtils;-%3EisPotentialEmergencyNumber(ILjava%2Flang%2FString;Ljava%2Flang%2FString;)Z

-removes unnecessary internal helper functions (no functional change)
Fixes: 225397721
Test: Unit tests
Change-Id: I846805084fd0a1b29d9dd9c01f61da38ea97fd08