Add rabbitmq streaming sample

[onobc]

Create sample illustrating how to use SCS rabbitmq streaming binder with SCDF.

cc: @markpollack

[onobc]

Let's be sure to include documentation w/ the sample in the repo.

[garyrussell]

@onobc See spring-cloud/spring-cloud-stream-samples#213

Bear in mind that RabbitMQ stream queues are somewhat limited - no scale out - yet.

RabbitMQ 3.11 (fall 2022) adds support for competing consumers; it's now available as alpha (I was just told this morning). I am planning on looking at it in the next couple of weeks.