Test that mixed retention & compaction work in the CLI

[thody]

KIP-71 introduces the ability to mix compaction and retention clean-up strategies for topics.

For Kafka MT, where compaction is enabled, we also want to force a retention strategy to be enabled. Current thinking, has a standardized retention time for some plans, and the ability to select within a range for higher-end plans.

Depends on: https://trello.com/c/ErNbXA5C/747-kip-71-expose-topic-clean-up-capabilities-at-cluster-level-via-shogun-api

[idan]

Most of this has nothing to do with MT, we have to update the validation rules for mixing compaction and retention, can add the MT validation in a separate pull.

[tom-pang]

@idan there's a capabilities field in shogun's /data/kafka/v0/clusters/:id endpoint now, with a key supports_mixed_cleanup_policy - if that key is true, then this feature works for that version of Kafka. It only works on very new clusters for now.

[idan]

This should work — the CLI doesn't check to see whether both retention and compaction is specified, and shogun will error if it's busted.