Improve UX Around Arch Flag Validation

User Story:

As a user of HyperShift, I would like the UX around the `arch` flag validation improved so that it results in a smoother UX experience. The problem today is we default Arch to `amd64`, but then throw an invalid status message on the NodePool CRD if it's not blank and the platform is not AWS.

Acceptance Criteria:

DEFINE once path forward decided; SEE Engineering Details for more details.

Description of criteria:

(optional) Out of Scope:

Detail about what is specifically not being delivered in the story

Engineering Details:

At a minimum we should remove the empty `Arch` flag check here.

What about modifying the section to something like this:

// Validate modifying CPU arch support for platform
if (nodePool.Spec.Arch != "amd64") && (nodePool.Spec.Platform.Type != hyperv1.AWSPlatform) {
    SetStatusCondition(&nodePool.Status.Conditions, hyperv1.NodePoolCondition{
       Type:               hyperv1.NodePoolValidArchPlatform,
       Status:             corev1.ConditionFalse,
       Reason:             hyperv1.NodePoolInvalidArchPlatform,
       Message:            fmt.Sprintf("modifying CPU arch from 'amd64' not supported for platform: %s", nodePool.Spec.Platform.Type),
       ObservedGeneration: nodePool.Generation,
    })
} 

This requires/does not require a design proposal.
This requires/does not require a feature gate.