Add e2e tests for the Redis cluster

[voltbit]

• All K8s resources are up (operator deployment, pods, configmap, rediscluster, rbac, clusterrole, serviceaccount, services)
• The operator can handle multiple cycles of creation-destruction of the RedisCluster resource
• Specific scenario: after deleting the rdc resource all pods will be in Terminating state, check what happens if the rdc object is recreated imediately without waiting for all pods to disappear - this must be handled by the operator (ignore pods that are in Terminating state)
• Connectivity issue test: we should cut the network of the cluster and see how the operator handles it, it is not expected to fix anything but it must be able to function properly after network is back up and must not apply any unncesseary operations to the Redis cluster
  We will add more advanced testing that account for failure when we have the auto-recovery features implemented, for the moment we should have checks that guarantee that a simple, unperturbed operator run correctly creates the Redis cluster. These checks should later be used as validation in more complex, real-life scenario tests.