Wizard v6 - Consider making WizardBody required

[thatblindgeye]

Describe the enhancement or change
Followup based on comment chain #10285 (comment)

Currently a consumer could have the WizardBody omitted by passing a body={null] to a Wizard Step. This can cause an issue in the fix implemented in the above PR, but also Core marks the WizardBody elements as required. We should consider removing the ability for a consumer to prevent those components from rendering both to match Core and to always have a static element that can be focused via the above PRs fix.

Is this request originating from a Red Hat product team? If so, which ones and is there any sort of deadline for this enhancement?

Any other information?

[thatblindgeye]

Closes by #10637