KIP-1143 — Deprecated Optional<String> and return String from public Endpoint#listenerName

Accepted Kafka 4.1 ProtocolAdmin

Deprecates the Optional<String> return type of org.apache.kafka.common.Endpoint#listenerName() and changes it to return a plain String. The Optional was introduced because Endpoint was designed for both server-side and client-side use where listenerName could be null, but client-side usage was removed, making the Optional unnecessary and inconsistent with the internal EndPoint class that already returns String.

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