KIP-715 — Expose Committed offset in streams

Accepted Kafka 3.0 StreamsMetrics

Adds `committedOffsets()`, `endOffsets()`, and `timeCurrentIdlingStarted()` to `TaskMetadata` so health-check services can track per-task consumer progress without embedding Kafka clients. Kafka Streams embeds multiple consumer clients internally, making it impossible to derive task-level lag from the standard committed-offset APIs used for standalone consumers.

Details