Now that we support running DKG using the server with #218 we need to update it to use broadcast channel in the first round as required by the protocol.

We'll use Goldwasser-Lindell echo broadcast which is the simplest one.

Note that this is not sufficient to address ZcashFoundation/frost#577 which will done later on, probably when https://github.com/BlockstreamResearch/bip-frost-dkg is closer to done