KIP-761 — Add Total Blocked Time Metric to Streams

Accepted Kafka 3.1 StreamsMetrics

Introduces a new `blocked-time-total` metric in Kafka Streams that accumulates the total wall-clock time a stream thread spends blocked waiting on Kafka (poll, commit, flush) rather than processing records. Existing metrics like `poll-ratio` and `processing-ratio` are instantaneous ratios from a single poll loop iteration and are too coarse-grained to identify systemic blocking bottlenecks.

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