DO NOT MERGE Rename classes to match master

In preparation for backporting changes and tests from master, rename /
refactor some classes:

1) Rename NewNitzStateMachine -> NitzStateMachineImpl

2) Extract interface for NitzStateMachine.DeviceState / add
NitzStateMachine.DeviceStateImpl

3) Rename NewTimeServiceHelper -> TimeServiceHelper /
TimeServiceHelperImpl to match the src in master to enable easier
backporting.

Bug: 144757081
Test: Treehugger
Merged-In: I81ad0c324dab64913b943a20b3e9e30e344b0c92
Change-Id: Iebf64d4ea2b667e47cfa5f715b36008c1c3455df