IBC Communication Between Heterogeneous Paxos Chains and Main Chains With Bounded Latency

[isheff]

When our nodes can simultaneously run main chains and Heterogeneous Paxos Chains between them, we want to communicate between chains easily, and with bounded latency (as measured in blocks). Since nodes participating in Heterogeneous Consensus are also participating in main chain consensus, this should be possible.
We should probably implement this using IBC bridges.