In certain cases, an AWS cluster running 4.12 doesn't automatically generate a controlplanemachineset when it's expected to.

It looks like CPMS is looking for `infrastructure.Spec.PlatformSpec.Type` (https://github.com/openshift/cluster-control-plane-machine-set-operator/blob/2aeaaf9ec714ee75f933051c21a44f648d6ed42b/pkg/controllers/controlplanemachinesetgenerator/controller.go#L180) and as result, clusters born earlier than 4.5 when this field was introduced (https://github.com/openshift/installer/pull/3277) will not be able to generate a CPMS.

I believe we should be looking at `infrastructure.Status.PlatformStatus.Type` instead

4.12.9

Consistent

1. Install a cluster on a version earlier than 4.5
2. Upgrade cluster through to 4.12
3. Observe "Unable to generate control plane machine set, unsupported platform" error message from the control-plane-machine-set-operator, as well as the missing CPMS object in the openshift-machine-api namespace

No generated CPMS is created, despite the platform being AWS

A generated CPMS existing in the openshift-machine-api namespace