Refactor Consume API to work for Native Kafka

[rohitsanj]

Summary of Changes

Refactor Consume API to work for Native Kafka rather than specifically for Confluent Local. This will be useful once we wish to consume topics using the yet-to-be-added "Direct" connection types.

Functional changes

We now try to JSON parse non-schema'd record key/value data instead of returning the string representation of it. A few tests have been updated to reflect this change.

Any additional details or context that should be provided?

Pull request checklist

Please check if your PR fulfills the following (if applicable):

• Tests:
  • [ ] Added new
  • [x] Updated existing
  • [ ] Deleted existing
• [x] Have you validated this change locally against a running instance of the Quarkus dev server?

  make quarkus-dev

• [x] Have you validated this change against a locally running native executable?

  make mvn-package-native && ./target/ide-sidecar-*-runner

[rohitsanj]

@rhauch @flippingbits I've added some explanatory/clarifying documentation in the latest commit. Please have a look, thanks!