Add flag to stats-log-api-gen for WorkSource.

As part of getting rid of StatsLogInternal and moving every atom to be
logged from a module, this CL addresses 2 issues:
1. Add WorkSource logging to modules.
2. Gate WorkSource logging via a CLI flag to prevent WorkSource methods
from being included in modules that are Mainline modules and can't have
@hide calls.

Bug: 147541828
Test: m
Test: atest android.cts.statsd.atom.UidAtomTests

Change-Id: Icce2f6ed7298be5e5ceebfb05d87e6fa7cd6bdbb
Merged-In: Icce2f6ed7298be5e5ceebfb05d87e6fa7cd6bdbb