KIP-717 — Deprecate batch-size config from console producer

Discarded Kafka 4.2 ProducerAdmin

Deprecates the `--batch-size` option from `kafka-console-producer.sh` since the new producer does not batch by message count, making the option a no-op. The option was a holdover from the old producer API and misleads users into thinking count-based batching is active when it is not.

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