KIP-690 — Add additional configuration to control MirrorMaker 2 internal topics naming convention

Accepted Kafka 3.1 MirrorMaker

KIP-690 adds `heartbeatsTopic()`, `checkpointsTopic(clusterAlias)`, and `offsetSyncsTopic(clusterAlias)` methods to the `ReplicationPolicy` interface so MirrorMaker 2 internal topic names can be overridden via `replication.policy.separator` or a custom `ReplicationPolicy` implementation. The previous hardcoded names (`heartbeats`, `<alias>.checkpoint.internal`, `mm2-offset-syncs.<alias>.internal`) could not be changed, blocking deployment in clusters that enforce topic naming conventions or prohibit auto-topic creation.

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