Remove instance fields from MobileSignalController

MobileSignalController (MSC) was storing a few fields as instance
members on itself, and thus would lose that historical information and
make it so logs could not give the full picture of what the state was in
the past

This change makes a couple of changes to make things simpler:

1. Move all telephony data onto the MobileState object, making it so the
   full decision-making state object is stored at every historical level
2. Attach MobileState and MobileStatus directly so MobileState reads its
   fields directly from the update
3. Log only the used fields from ServiceState and SignalStrength

Things are in a much better state here, but the next step should be to
formalize the difference between the fields that get set directly from
MobileStatus, and the ones that are updated in MSC#updateTelephony

Test: atest SystemUITests
Bug: 197851948
Change-Id: Ia35a13ee36b8e41b9ca86506de56f98de4891006