Core scheduler relies on a special table in the state store—the TimeTable—to
figure out which objects can be GC'd. The TimeTable correlates Raft indices
with objects insertion time, a solution we used before most of the objects we
store in the state contained timestamps. This introduced a bit of a memory
overhead and complexity, but most importantly meant that any GC threshold users
set greater than timeTableLimit = 72 * time.Hour was ignored. This PR removes
the TimeTable and relies on object timestamps to determine whether they could
be GCd or not.
f7847c6e5b