Separate AccessNetworkManager from TransportManager

Moved partial TransportManager logic into AccessNetworksManager.
This is the preliminary step to remove TransportManager in data
redesign.

Bug: 196597630
Test: atest FrameworksTelephonyTests & manual test
Merged-In: I679368636b97a49814bbfec362c06b419a27af37
Change-Id: I679368636b97a49814bbfec362c06b419a27af37