Distinguish 'primary' and 'secondary' role owners where appropriate about proposals

[ManfredKarrer]

We probably should apply that to the seed nodes, prices nodes, btc nodes to have a backup of the onion keys. So in that case the secondary would only keep a copy of the onion key and could in emergency case step in by starting up a own service. No need to share access to the actual machines as if a new onion service is published the new one will be picked anyway in case the old one would still be running.

[cbeams]

Closing as approved. We're still rolling this change out across the various roles. In any case, I'll capture the decisions made here when I write up the doc on roles (bisq-network/bisq-docs#46).