Add test to verify topological ordering of EventSet

Add test to verify topological ordering of EventSet

The topological ordering was moved into EventSet
in a prior commit since it is useful to order
events in an EventSet that reside outside of a
Configuration. This commit adds a stress test
that verifies that the topological orderings
of all possible subsets of a collection of
events obey the topological ordering invariant
after being ordered (in both directions)