1. migrate set/get roamingType from ServiceState to
NetworkRegState.set/get roamingType
2. migrate set/get roamingStateFromRegstate from ServiceState
to NetworkRegState.regState
3. new System API for neworkRegistration.isRoaming().
Bug: 116127096
Test: ServiceStateTest, ServiceStateProviderTest
Change-Id: Ib89744089c98713819c8d313240d629ddb77d0bf