config: failover mode and election mode consistency

[TarantoolBot]

Related dev. issue(s): tarantool/tarantool#9431
Related doc. issue(s): https://github.com/tarantool/enterprise_doc/issues/253

Product: Tarantool
Since: 3.0
Root document: https://www.tarantool.io/en/doc/latest/reference/configuration/configuration_reference/#configuration-reference-replication-election-mode
SME: @ Totktonada

Details

replication.failover: election enables RAFT based leader election
mechanism on a replicaset. The instances can be configured in the
following election modes: off, candidate, voter, manual. It is
controlled by the replication.election_mode parameter.

However, the election mode parameter has no sense and confusing for
other failover modes (off, manual, supervised). So, it is
forbidden to set the election modes other than off in failover
modes != election.

Summary:

• replication.failover: off
  • replication.election_mode: off: OK
  • replication.election_mode: candidate: FAIL
  • replication.election_mode: voter: FAIL
  • replication.election_mode: manual: FAIL
• replication.failover: manual
  • replication.election_mode: off: OK
  • replication.election_mode: candidate: FAIL
  • replication.election_mode: voter: FAIL
  • replication.election_mode: manual: FAIL
• replication.failover: election
  • replication.election_mode: off: OK
  • replication.election_mode: candidate: OK
  • replication.election_mode: voter: OK
  • replication.election_mode: manual: OK
• replication.failover: supervised
  • replication.election_mode: off: OK
  • replication.election_mode: candidate: FAIL
  • replication.election_mode: voter: FAIL
  • replication.election_mode: manual: FAIL
    Requested by @ Totktonada in tarantool/tarantool@a03064b.