KAFKA-15995: Initial API + make Producer/Consumer plugins Monitorable

[mimaison]

First part of KIP-877.

This adds the public APIs and enables the following plugins:

• Serializer
• Deserializer
• ProducerInterceptor
• ConsumerInterceptor
• Partitioner which are all the Producer and Consumer specific plugins.

Committer Checklist (excluded from commit message)

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