New command: stream-perf-test

[mkuratczyk]

This allows running stream-perf-test easily, for example:

kubectl rabbitmq stream-perf-test INSTANCE --rate 100

Notes for reviewers: due to yesterday's default port changes, you need to run the Operator from main to use port 5552 and a very fresh RabbitMQ image, for example:

apiVersion: rabbitmq.com/v1beta1
kind: RabbitmqCluster
metadata:
  name: stream
spec:
  replicas: 1
  image: pivotalrabbitmq/rabbitmq-stream
  rabbitmq:
    additionalPlugins:
      - rabbitmq_stream