Generate validation block for CRDs in OLM catalog

[ericavonb]

Add validation schema to the custom resource definitions generated for the OLM catalog.

[spahl]

This will need a bit of design

[mattmb]

As a newbie I was surprised that this didn't exist already and that it was only a recent addition to k8s itself. It'd be great if running the generate command added the validation section to the YAML definition of the CRD.