Create framework-statsd

Create framework-statsd jar in statsd apex.
Move StatsEvent to framework-statsd.jar.
Right now, frameworks jar links against framework-statsd directly. This
should be changed to link against framework-statsd-stubs.

Bug: 145923096
Bug: 145923116
Bug: 142810493

Test: m
Test: flashes successfully
Test: adb shell cmd stats print-logs && adb logcat "*:S statsd:*"

Change-Id: Ife224abd5c9b9b0eeab681dc4b7f71c0bdb856b1