Draft of [Syncing KeyserverStore without keyserver](https://linear.app/comm/issue/ENG-5441/syncing-keyserverstore-without-keyserver) goal. Implemented because it was really tough to test [Broadcasting information to peers](https://linear.app/comm/issue/ENG-7398/[may]-broadcasting-information-to-peers) with syncing actual data. Publishing this now to share with reviewers more insight into test plans and show the general approach.
This diff is going to be sliced into smaller ones and improved.
Depends on D12132