KIP-723 — Add socket.tcp.no.delay property to Kafka Config

Discussion Broker

Makes `TCP_NODELAY` configurable on broker sockets (defaulting to off for inter-broker communication) to reduce packet-per-second rates on clusters with large numbers of partitions. With `TCP_NODELAY` always enabled, a 4-broker cluster with 30,000 partitions generated ~140,000 TCP packets/second at load because each inter-broker heartbeat was sent as a separate small packet, triggering traffic-shaper limits in cloud environments.

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