Investigate refactoring Openshift Virtualization as a resource attribute

As pointed out by @naved001 [here](https://github.com/nerc-project/coldfront-plugin-cloud/pull/232#discussion_r2270909378), virtualization is an feature that can be optionally used in an Openshift cluster. Therefore, it makes more sense for it to be a resource attribute, rather than be a distinct resource type.

@knikolla What are your thoughts on this?