Set NetworkIdentity subscriberId on all networks

Instead of setting NetworkIdentity.subscriberId only on telephony
networks, set it when provided on any network. At the moment only
telephony is expected to have a subscriberId in its NetworkState anyway,
and while there are plans for other network agents (wifi) to have a
subscriberId, it should also be set in that case.

This allows NetworkIdentity to stop depending on hidden network type
APIs to determine if the network is mobile.

Bug: 174436414
Test: atest FrameworksNetTests
Change-Id: I4f09987f8737d1801342eb5d6d7c2b9968b466b0