[SM10] Adopt helper class to monitor RAT type change per sub

Test: atest NetworkStatsServiceTest
Bug: 146415925
Change-Id: I45c3aa9046b316c8cd0943543d620a22e4afefd1
Merged-In: I45c3aa9046b316c8cd0943543d620a22e4afefd1
(cherry picked from commit 219faff07bdc58c14fe58fc525e86383db1f8167)
2 files changed