Remove StateConditionTracker from statsd

StateConditionTracker was previously used as a way to slice by state
through a specific SimplePredicate definition. It is currently being
replaced by StateTracker, and no metrics use StateConditionTracker at
this time.

Bug: 136566566
Test: bit statsd_test:*
Change-Id: I1a14747907c23482a1b7500c6d7f07cd2f1d4aed