Add sysui module for logging SystemUI atoms.

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 SysUiStatsLog to SystemUI and replaces usages
of StatsLog with SysUiStatsLog.
Since the write calls in SysUiStatsLog are public, StatsLogCompat is no
longer needed.

Bug: 145952197
Test: m
Test: fastboot flashall
Test: adb shell cmd stats print-logs && adb logcat "*:S statsd:*"
Change-Id: I192ff29d21cedbe715bb02ffa05921b4912af371