Create separate scheduler Helm chart

This should allow us to more easily manage the scheduler in isolation from CTA (and vice-versa).

The Scheduler Helm chart would not spawn pods in and of itself, but it can generate the ConfigMap(s) needed by the CTA chart. Note that this then won't be fully independent, as the CTA chart still has some logic related to the scheduler that is not covered by the ConfigMap. These include:

• The mounting of Ceph-related volumes in case Ceph is used
• The cta.objectstore.backendpath in the cta-frontend-xrootd.yaml configmap
• The ObjectStore BackendPath in the cta-taped.yaml in the cta-taped.yaml configmap

In theory the last two could be resolved by looking into the scheduler ConfigMap, but this has not been implemented yet