Take 2: Integrate StateTracker into statsd

Changes in this CL compared to previous StateTracker version:
- MetricsManager parses StatsdConfig for State information and updates
MetricProducers accordingly
- MetricProducer implements StateListener
- MetricProducer has a list of atom ids of its slice_by_states and any
state maps from these states. MetricProducers are responsible for
handling the conversion from original state value to mapped state value.
- More unit tests added and e2e CountMetric test added

Test: bit statsd_test:*
Bug: 136566566
Change-Id: I07ce468733a1affcadf2be0206e081fddbbce4c5