raft: replication test: split elect_new_leader for prevote
raft: replication test: split elect_new_leader for prevote

Branch URL: https://github.com/alecco/scylla/tree/raft-fixes-02-v3-01

Tests: unit ({dev}), unit ({debug}), unit ({release})

This fixes current election hangs in next.

Message-Id: <7e793d2e3fb1ce70b36b2ac3c71fa613f882721c@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla