1. current connection is mobile data
- remove the SubscriptionsPreferenceController#activeNetworkIsCellular() and move into MobileNetworkUtils
2. isProviderModel API
- Add it in Util for Provider Model
3. isWiFiCallingEnabled
- remove WifiCallingPreferenceController#isWifiCallingEnabled() and move into MobileNetworkUtils
4. Add nes test case for MobileNetworkUtils
Bug: 171873895
Test: atest -c MobileNetworkUtilsTest
Change-Id: I4bfdf0537fe07d064d6c0ba4a2c44b4a4f158d91