Currently, the ClusterImageSet resource depends on the (optional) InstallConfig only so that we can set the correct namespace for it in the metadata, and have this be consistent with other resources generated from the InstallConfig.

If the InstallConfig is not provided, we will refuse to generate the ClusterImageSet. We should instead generate it with an empty namespace, since the namespace data is not even used by the agent installer. (There is a danger of generating invalid ZTP manifests and the user then trying to use them with ZTP. But the InstallConfig must be provided to generate the rest of the manifests anyway.)

Note that ClusterImageSet cannot depend on another of the cluster-manifests, because if it did then a user importing their manifests from ZTP would see this one get silently overridden with the version corresponding to the the installer binary. This should be an explicit choice.

Allowing this asset to be generated without an install-config will allow the user to provide only the InfraEnv and AgentPullSecret resources when creating the unconfigured Ignition in AGENT-558.

Acceptance Criteria:

• the unconfigured ignition can be generated without user providing install-config.yaml
• integration test to verify that uconfigured ignition can be generated without install-config