Configurable compression level

[bobrik]

Currently there's no way to configure compression level for Gzip. We also want to add Zstd support to Kafka itself, where there are many compression levels:

• KAFKA-4514: Add Codec for ZStandard Compression apache/kafka#2267

There should be a setting to set compression level in producer config. I'm not sure whether we want separate config per codec (CompressionLevelGZIP, CompressionLevelZSTD) or one setting to rule them all (CompressionLevel). The former seems more flexible.

[eapache]

Separate config does feel more flexible, but given that gzip, zstd, and all other compression codecs I can think of specify levels in simple integers, a single CompressionLevel seems sufficient? There's currently no way to specify multiple compression codecs in a single config, so there should never be any ambiguity.