[kafka] Handle basic Produce requests independently of storage

[gyang94]

Purpose

Part of #4185. PR05 of the Kafka compatibility sequence.

Implement non-idempotent Produce v3-v11 with a narrow backend contract. Validate acknowledgements, topic/partition identities and record batches; isolate invalid partitions, preserve response order and copy record data independently of the network buffer.

Acceptance criteria

• Valid requests preserve records, headers, listener context, acks and timeout.
• Invalid batches and topics do not suppress valid partitions in the same request.
• Transactional/idempotent/control batches and duplicate partition entries are rejected.
• acks=0 emits no response and releases the request buffer on success and failure.
• Production ApiVersions continues to expose only the existing capabilities until append is integrated.

Dependencies

PR04 Metadata (#4261 / #4266).

Scope boundary

No row conversion, gateway append or production Produce registration.

Implementation

Draft PR #4284: #4284

Java 11 validation: 69 unit tests and 2 integration tests passed at 936fd3f39e9e6fe595ed6bf8e30f0e2b5185ffe3. Review and merge remain pending.