KIP-510 — Metrics library upgrade

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KIP-510 proposes upgrading Kafka's internal metrics library from the abandoned Yammer Metrics 2.2.0 to Dropwizard Metrics 4.x, gaining bug fixes, JDK 9+ support, and improved reservoir implementations. The current library has not been maintained since 2012, lacks support for modern JDK features, and contains known bugs that the newer version addresses.

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