Add 3C3D IoTConsensusV2 integration tests

[Pengzna]

Add IT for IoTConsensusV2 on a 3 ConfigNode + 3 DataNode cluster.

Tests:

1. test3C3DWriteFlushAndQuery: Start 3C3D cluster, write data, flush, and verify data via query.
2. testReplicaConsistencyAfterLeaderStop: With replication factor 2, stop the leader DataNode and verify the former follower (new leader) serves the same data after failover.

Implementation details:

1. Config: IoTConsensusV2 batch/stream mode, DataReplicationFactor=2, SchemaReplicationFactor=3.
2. Uses getConnection(followerNode) to query the specific follower instead of a random available node.
3. Extends IoTDBRegionOperationReliabilityITFramework for getDataRegionMapWithLeader and cluster setup/teardown.
4. Uses getString() in verifyDataConsistency for IoTDB JDBC compatibility.

[jt2594838]

This is very unstable in the test environment; it is better to check the data directory of each node to ensure that two nodes have the associated TsFiles.

[jt2594838]

Killing the node may result in losing some unflushed data.
Although you may have called FLUSH previously, the data may not have been synchronized then, so the FLUSH command may not work on the follower.
You should first wait until the unsealed TsFile appears on the follower, and then FLUSH.