Test trigger acquisition logic

[lukeryannetnz]

The core logic around which triggers to fire, including the cluster locking/scheduler logic is contained in two large, complex methods:
AcquireNextTriggers
ApplyMisfireIfNecessary

We need decent test coverage over these to assert they are behaving correctly before we can refactor/change them. It would also be nice to have confidence that the dynamo conditional writes used to implement distributed locks are working as desired.

[lukeryannetnz]

@ddhi004 if you want a challenge, this requires a fair amount of mental enterprise.