KIP-722 — Enable connector client overrides by default

Accepted Kafka 3.0 Connect

Changes the default value of `connector.client.config.override.policy` from `None` to `All`, enabling connector-level client configuration overrides by default in Kafka 3.0. The original default of `None` was chosen conservatively for backward compatibility, but left the KIP-458 per-connector client override feature effectively disabled out of the box.

Details