[Dexter] Enable after_hit_count for state nodes
The after_hit_count attribute for a state node causes it to become active
only after it would have become active N times. This uses the existing logic
for incrementing hit counts, i.e. after the node becomes "active", we will
not add another hit count until it stops being active for at least one step.
Since state nodes with after_hit_count do not become active before reaching
the required hit count, this requires us to keep track of an "early" set of
state nodes, meaning nodes that would be active if not for their
after_hit_count.
