Milvus CDC Standby Cluster Replication

Milvus introduces built-in Change Data Capture (CDC) for primary-standby replication, enabling cluster-level and cross-region high availability. This feature streams Write-Ahead Log (WAL) entries from a primary cluster to a standby cluster, allowing for near real-time data synchronization. The standby cluster can be promoted in case of primary cluster failure, minimizing downtime and data loss. This complements node-level replication and periodic backups for a layered HA strategy. The initial implementation supports single CDC replica and does not support BulkInsert.