Redesign JMS-source as a standalone Supplier function

[sabbyanandan]

Builds upon the findings from https://github.com/spring-cloud-stream-app-starters/app-starters-release/issues/219 and https://github.com/spring-cloud-stream-app-starters/app-starters-release/issues/220.

• [ ] Port the app -> supplier function
• [ ] Add tests
• [ ] Generate App from the supplier function
• [ ] Run end-to-end tests in SCDF

[sabbyanandan]

Outstanding questions:

• Concurrency: If we move with reactive/functional style, how do we deal with concurrency?
• Convert it to a fully functional app (requires SCSt 3.3 M3)

[sabbyanandan]

Closing this in favor of https://github.com/spring-cloud-stream-app-starters/app-starters-release/issues/222.