KAFKA-17091: Add @FunctionalInterface to Streams interfaces

[raymcdermott]

Goal

Add @FunctionalInterface to Streams interfaces to enable Clojure 1.12 (and any other JVM language) to have the correct hints for these SAM interfaces.

The Clojure issue is here

Testing

Unit tests and system tests all pass locally.

Committer Checklist (excluded from commit message)

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

[bbejeck]

Hi @raymcdermott thanks for the PR! Since this is a change to the public interface code of Kafka Streams, this PR will require a KIP. Ping me here once you create a wiki ID (step 2 in the getting started section from the page referenced above) and I'll go in and give you edit permissions to create a KIP.

[mjsax]

It seems ForeachAction is missing?

Also wondering about TransformerSupplier (and siblings) -- are they not effectively deprecated via https://cwiki.apache.org/confluence/display/KAFKA/KIP-820%3A+Extend+KStream+process+with+new+Processor+API (even if the KIP does not say so expliclity -- what might be a miss on our end to add to the KIP... Thoughts)

What about other PAPI interfaces like FixedKeyProcessor, api.Processor (not sure if both quality or not), Punctuator, StateRestoreCallback (maybe?), StreamPartitioner, TimestampExtractor, TopicNameExtractor, and IQ interface Query?

Not sure if there might be other I have missed.