1. Fix primary-secondary replication switchover blocking by delete
replicate pchannel meta using modRevision.
2. Stop channel replicator(scanner) when cluster role changes to prevent
continued message consumption and replication.
3. Close Milvus client to prevent goroutine leak.
4. Create Milvus client once for a channel replicator.
5. Simplify CDC controller and resources.
issue: https://github.com/milvus-io/milvus/issues/44123
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Signed-off-by: bigsheeper <yihao.dai@zilliz.com>
