KIP-271 — Add NetworkClient redirector

Discussion Client

KIP-271 proposes a `NetworkClientRedirector` plugin interface that intercepts broker address resolution in `NetworkClient`, allowing clients to remap internal broker hostnames to externally reachable addresses. Clients connecting to Kafka from outside a private network (e.g., from outside Kubernetes or AWS VPC) fail after the initial bootstrap because subsequent metadata responses contain internal DNS names unreachable from the client.

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