Migrate to SettingsStatsLog from StatsLog

As part of statsd becoming a Mainline module in R, autogenerated
StatsLog.write() calls are going away and replaced by *StatsLog.java
that is autogenerated for each module.
This CL adds autogenerated SettingsStatsLog and replaces usages
of StatsLog with SettingsStatsLog.

Bug: 145952197
Test: m
Change-Id: I3ffdb51394017e3e48b65734d67595abd69dd70d