Proposed title of this feature request

Support HCP control-plane on s390x (Z-Systems)

What is the nature and description of the request?

Currently we have a TechPreview of mixed Clusters for HCP for Z (s390x). In this case the control plane is hosted on x86 using HCP and IBM Z nodes are added to the cluster (https://docs.redhat.com/en/documentation/openshift_container_platform/4.16/html/hosted_control_planes/getting-started-with-hosted-control-planes#hcp-getting-started-ibmz) 

The Customer asks for a "pure Z" support of HCP.

Why does the customer need this? (List the business requirements here)

• First case: We would like to offer our internal customers (e.g. developers, application admins) OpenShift as a Service. With the help of HCP we could do this much easier and more leightweight than setting up a complete cluster for every customer. Especially because on Z we have to do UPI which adds complexity. Currently we offer Namespace as a Service and we would like to extend our offering.
• Second case: Our datacenter has multiple network zones to realize security and multi tenancy. With HCP we could set up leightweight clusters in different network zones to support multi tenancy. This would be also much easier and faster than setting up complete clusters.
• With the cases from above, we could enable more developers, application admins to try OpenShift and, finally, use OpenShift. So we can increase the workload on our IBM Z to make it affordable. With HCP we could use our IBM Z much more efficiently.
• Currently, we build a new data center, where OpenShift as a Service is a requirement, e.g., for Ansible Automation Platform. HCP would help our IBM Z OpenShift team to have more opportunities in the future.
• $CUSTOMER is part of the „Deutsche Verwaltungscloud“ and there are also requirements for Kuberentes as a Service, which would be much simpler to realize with HCP.

 List any affected packages or components.

• Hosted Control Planes