Simplify KafkaConsumer constructor logic

[nresare]

This mirrors how the KafkaProducer constructors are organised and reduce
code duplication.

More specifically this PR makes the following changes without changing any behaviour or public API:

1. Move the helper method propsToMap() from KafkaProducer to Utils with the other
   similar helpers mkMap() and mkProperties(), as this is now both used by KafkaConsumer and KafkaProducer.
2. Move the ConsumerConfig instantiation to the constructor that actually does the work.
3. Remove the addDeserializerToConfig() that operates on Properties and it's two tests, as all of those are very similar to the ones that operate on Map<String, Object> instances.
4. Have the KafkaConsumer constructors that accept Properties parameter convert those early to Map<String, Object> instances.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[chia7712]

It seems #8605 is duplicate to this issue.

[nresare]

@chia7712 what an interesting coincidence that our changes looks almost identical although I can assure you that they have been developed completely independently

[ijuma]

Closing in favor of #8605.