KIP-1307 — SerDe and Interceptor Metrics

Discussion ClientMetrics

Adds client-side sensors for serialization/deserialization and interceptor execution: timing metrics at DEBUG recording level, plus per-key/value size and error rate/total metrics at INFO, tagged by serializer/deserializer class and key-vs-value type. Serde and interceptor code runs in the hot path with no instrumentation, so a schema change turning a 200us deserialization into 2ms, or a slow custom serde calling a schema registry, is indistinguishable from broker or network latency.

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