GKE load testing, controller pod, pubsub updates

[wajihyassine]

• Add a Turbinia controller docker build/k8s file used for troubleshooting and accessing direct logs
• Move shared k8s resources between GKE pubsub and celery to a common folder and removed duplicates
• Create load testing script for performance testing/troubleshooting GKE related issues
• Add turbinia api server in default deployment to GKE celery
• Update deploy-pubsub-gke.sh script with some structure changes, similar to what was done for celery deploy scripts
• Documentation around deploying Turbinia controller and running load tests
• Renaming cleanup to destroy
• Added more helpful aliases for common k8s commands