1/ Support nested message and repeated fields in statsd.

2/ Filter gauge fields by FieldMatcher.
3/ Wire up wakelock attribution chain.
4/ e2e test: wakelock duration metric with aggregated predicate dimensions.
5/ e2e test: count metric with multiple metric condition links for 2 predicates and 1 non-sliced predicate.

Test: statsd unit test passed.

Change-Id: I89db31cb068184a54e0a892fad710966d3127bc9