KIP-1058 — Txn consumer exerts pressure on remote storage when reading non-txn topic

Accepted Kafka 4.0 Tiered StorageTransactions

KIP-1058 adds a `txnIdxEmpty` tagged field to `RemoteLogSegmentMetadataRecord` and `RemoteLogSegmentMetadataSnapshot` so the Remote Log Manager can skip fetching remote transaction indexes for segments that have no aborted transactions. When `isolation.level=READ_COMMITTED` consumers fetch from topics with no aborted transactions, the broker currently scans all remote segment transaction indexes sequentially before reaching local segments, causing excessive remote storage API calls and increased fetch latency.

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