KIP-1235 — Correct the default min.insync.replicas to 2 for the __remote_log_metadata topic

Discussion Kafka 4.3 Tiered StorageBroker

Adds a new broker config remote.log.metadata.topic.min.isr (default 2) that is applied as min.insync.replicas when creating the __remote_log_metadata topic. Without an explicit min.isr, the topic defaulted to 1, meaning a single-broker failure in a 3-replica setup could cause tiered storage metadata loss and render remote data unreachable even though it still exists in object storage.

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