Add keycloak sso test for Grafana Prometheus and alertmanager

Grafana:

• Add SSO login to the Grafana test
• Add SSO login to the Istio/grafana test
• Add SSO login to the Prometheus test
• Write a basic Alertmanager test
  • which can log in with SSO if enabled

Note: There is currently no basic cypress test for alertmanager. One can be written here that logs in with SSO and looks at the homepage or does some other basic check.