In the Raft-based recovery procedure, we create a new group 0 and add
live nodes to it one by one. This means that for some time there are
nodes which belong to the topology, but not to the new group 0. The
voter handler running on the recovery leader incorrectly considers these
nodes while choosing voters.
The consequences:
- misleading logs, for example, "making servers {<ID of a non-member>}
voters", where the non-member won't become a voter anyway,
- increased chance of majority loss during the recovery procedure, for
example, all 3 nodes that first joined the new group 0 are in the same
dc and rack, but only one of them becomes a voter because the voter
handler tries to make non-members in other dcs/racks voters.
Fixes#26321Closesscylladb/scylladb#26327
67d48a459f