KIP-256 — Add RocksDB statistics via Streams metrics

Discussion StreamsMetrics

Exposes RocksDB's internal `Statistics` metrics (block cache hits, compaction bytes, bloom filter hits, etc.) through the Kafka Streams metrics subsystem via a configurable `metrics.recording.level`. RocksDB's native stats are accessible only by directly manipulating internal `RocksDB` objects, which is not feasible for users using the Streams high-level DSL.

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