refactor data/voice roaming states

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: I792250509cb50b073f3149dd96dcf79276d0ddaa
2 files changed