Create a new installer subcommand, something like openshift-install agent create unconfigured-image. At least initially, this command should be hidden from the inline help, since we may choose to use it only as part of the backend of a web service and not support it more broadly.

This image will contain the unconfigured Ignition from AGENT-558 rather than the fully-configured Ignition of the automation workflow.

No changes will be made to the validation of the install-config to allow only the subset of data we actually use to be provided. This may be included in a future story if we decide to make the CLI command a public interface.