Remove @hide usages from statsd apex

- Slog -> Log
- Inline Context.STATS_COMPANION_SERVICE
- Inline Context.STATS_MANAGER_SERVICE
- Inline Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND. This is temporary.
Will use the approach in ag/10055770 in a follow-up CL.

Bug: 149128236
Test: m
Change-Id: I76f4b139d375f67c6d69b8494a9e843f773eeb09