crossplane resource validate: Add schema/definition dynamic location lookup

### What problem are you facing?

If non crossplane composite resources are part of an composition, the CRD of the manifest has to copied locally in order to that `crossplane resource validate` works.

### How could Crossplane help solve your problem?

The issue is resolved at kubeconform: The supports fetching the remote schema dynamically: `kubeconform -schema-location default -schema-location 'https://raw.githubusercontent.com/CustomResourceDefinition/catalog/main/schema/{{.Group}}/{{.ResourceKind}}_{{.ResourceAPIVersion}}.jso n'`

If only definitions instead schema will be supported, it wont be a issue, since the linked repository additionally contains definitions, e.g.: https://raw.githubusercontent.com/CustomResourceDefinition/catalog/refs/heads/main/definitions/argoproj.io/appproject.yaml