KIP-515 — Enable ZK client to use the new TLS supported authentication

Accepted Kafka 2.5 Security

Adds configuration properties (`zookeeper.ssl.client.enable`, `zookeeper.clientCnxnSocket`, `zookeeper.ssl.keystore.*`, `zookeeper.ssl.truststore.*`) to enable TLS-encrypted communication between Kafka brokers and ZooKeeper 3.5.x+. Previously, Kafka brokers could only communicate with ZooKeeper in plaintext, leaving ZooKeeper coordination traffic unencrypted even in security-hardened environments.

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