KIP-606 — Add Metadata Context to MetricsReporter

Accepted Kafka 2.6 MetricsClient

Adds a `ClientInformation` object to the `MetricsContext` passed to `MetricsReporter` plugins, exposing metadata about whether the reporting component is a broker, Connect worker, or client library (producer/consumer/admin/streams). Without this context, metric reporters could not determine which component was emitting metrics, making it impossible to route or label metrics correctly in multi-component deployments.

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