Decouple Fgs logic from UsageStats reporting logic

- The logic for Fgs will be different (For the PAUSED state) there
will be a time window before calling stopFgs.

- UsageStats reporting has its feature flag, so it shouldn't be hidden
by Fgs flag.

- Fgs will not support MediaSesson2 because it is not linkable to
notifciations, this doesn't apply to UsageStats reporting.

Bug: 295518668
Bug: 297052684
Test: Non functional change
Change-Id: If06fc75a7f83e49759264aa30cda3c7834bbf1b6