v.21.2Improvements

Update librdkafka to v1.6.0-RC2 and fix issues #18668 and #18671

Update librdkafka to v1.6.0-RC2. Fixes #18668. #18671 (filimonov).
Updated the integrated librdkafka library to version 1.6.0-RC2 in ClickHouse.

Why it matters

This update improves ClickHouse's Kafka integration by incorporating fixes and enhancements from librdkafka 1.6.0-RC2, addressing issues such as the one reported in issue #18668. It provides users with a more stable and reliable Kafka client implementation within ClickHouse.

How to use it

Users benefit from this update automatically by running the ClickHouse version that includes this librdkafka upgrade. No additional configuration is needed unless specific librdkafka features are used that require enabling in ClickHouse settings.