If no Cluster or Kubernetes Integration is present try to create one from Application Templates

Following issue for disabling the integration: https://gitlab.com/gitlab-org/gitlab-ce/issues/41054

We should allow to automatically create Clusters::Cluster from Kubernetes Integration Application Template.

The actual piece of code doing that is presented in this comment: https://gitlab.com/gitlab-org/gitlab-ce/issues/38668#note_49103753