KIP-886 — Add Client Producer and Consumer Builders

Discussion ClientProducerConsumer

Introduces a fluent builder API for `KafkaProducer` and `KafkaConsumer` with named methods, typed enum parameters, and Javadoc for each configuration option. The existing constructor takes an untyped `Properties` map, offering no IDE autocomplete, no type safety, and no discoverability of valid configuration values.

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