Add support to scrape and index metrics

This commit:
- Enables Kraken to leverage kube-burner to scrape metrics from
  Prometheus and index them into Elasticsearch. This way we can
  take a look at the metrics in Grafana long term even after the
  cluster is terminated.
- Enables separation of operations based on distribution with
  OpenShift as the default option. One of the use cases is to
  capture Prometheus instance details as it's installed by default
  while it's optional for Kubernetes.

README.md

@@ -36,6 +36,9 @@ It's important to make sure to check if the targeted component recovered from th
 ### Performance monitoring
 Monitoring the Kubernetes/OpenShift cluster to observe the impact of Kraken chaos scenarios on various components is key to find out the bottlenecks as it's important to make sure the cluster is healthy in terms if both recovery as well as performance during/after the failure has been injected. Instructions on enabling it can be found [here](docs/performance_dashboards.md).
 
+### Scraping and storing metrics long term
+Kraken supports capturing metrics for the duration of the scenarios defined in the config and indexes then into Elasticsearch to be able to store and evaluate the state of the runs long term. The indexed metrics can be visualized with the help of Grafana. It uses [Kube-burner](https://github.com/cloud-bulldozer/kube-burner) under the hood. The metrics to capture need to be defined in a metrics profile which Kraken consumes to query prometheus ( installed by default in OpenShift ) with the start and end timestamp of the run. Information on enabling and leveraging this feature can be found [here](docs/metrics.md).
+
 ### Blogs and other useful resources
 - Blog post on introduction to Kraken: https://www.openshift.com/blog/introduction-to-kraken-a-chaos-tool-for-openshift/kubernetes
 - Discussion and demo on how Kraken can be leveraged to ensure OpenShift is reliable, performant and scalable: https://www.youtube.com/watch?v=s1PvupI5sD0&ab_channel=OpenShift