Bump to Kafka client 2.1.0

[ppf2]

Kafka 2.1.0 was released on 11/20. This is an issue to track the bump of our Kafka input plugin to the 2.1.0 version of the client libraries.

[shaharmor]

Hey, any progress on this?

[danielmotaleite]

zstandard compressions is a killer feature ! :)

[ppf2]

2.1.0 client upgrade is available in logstash-input-kafka v8.3.0 (and above) per #300