Add workload and bootstrap preview

Add 2 new clusterTypes for bootstrap-preview and workload-preview.

This is a temporary quickFix, as this is required to rebase sylva-projects/sylva-core!4101 (merged) on top of sylva-projects/sylva-core!5011 (merged), and this is also required for workload-cluster-operator!300 (closed).

Ultimately, this feature will be covered by #52 (closed), but as it requires a significant rework, this change will unblock other MRs in the meantime.