Dispute Distribution Subsystem

[rphmeier]

We need information about disputes to propagate between nodes quickly - as soon as a validator observes a dispute, that information should propagate to others. As validators begin to participate in the dispute, those votes should also propagate through the network quickly. Disputes are rare and this protocol should probably be a flood-style protocol.

That said, there are a few spam/garbage vectors we'd like to mitigate:

• 2 colluding malicious validators can create an infinite amount of disputes where they contradict each other. This garbage should be avoided to keep the network free for legitimate traffic
• Ancient disputes, which have no relevance, should not be re-broadcasted.
• potentially others

[rphmeier]

Closed in #3158