Handle running hash syncronization without a Future

We currently handle thread synchronization between the running event hasher and the consensus round handler via a Future. This pattern is incompatible with turtle style testing.

Switch this into a wiring model managed join operation. The consensus round handler will need to accept consensus rounds and running hashes, and join them together into a single output stream (the immutable states). This is going to be more complicated that refactoring the PCES synchronization, since the join logic is going to have to live inside the consensus round handler directory (due to state immutability constraints).