Auto DevOps: Refuse to continue if opting into new postgres but we detect existing DB

Currently, we delete the old postgres, if you opt in to the new postgres (via AUTO_DEVOPS_POSTGRES_CHANNEL variable)

To make this a safe operation for those who were previously using Postgres version 1, we need to hard-stop if the following conditions are met:

• AUTO_DEVOPS_POSTGRES_CHANNEL is 2.
• We detect there was a previous deploy for the application (something like helm get "$name"?), or we detect that the old Postgres is installed (something like kubectl get pod --namespace "$KUBE_NAMESPACE" -l "app=${name}-postgres"?)
• AUTO_DEVOPS_POSTGRES_DELETE_V1 is not set