Integrate Questionnaire validator with new validator

[ewoutkramer]

@brianpos has written a Questionnaire validator, which could be integrated with the new validator.

When of the most important things to fix is aligning the validation result reporting in the validator with that in the Questionnaire validator. @ewoutkramer and @brianpos did some initial alignment during the September 2022 WGM, but those ideas have not been elaborated or finalized in code.