Include aggregated ClusterRoles from upstream manifests

[knkski]

Here are some ClusterRoles that are necessary for training-operator to work properly with a multi-user Kubeflow deployment:

https://github.com/kubeflow/manifests/blob/54aa7ae/apps/training-operator/upstream/overlays/kubeflow/kubeflow-training-roles.yaml

Right now, training-operator doesn't create them. Since it's a sidecar charm with full Kubernetes API access vs a pod spec charm, it can create them itself.