fix(GAT-9237): bug in the onboarding form for tools

[calmacx]

Screenshots (if relevant)

Describe your changes

• Fixes a bug ingenerateValidationRules (now in src/utils/formHydration.tsx) was silently dropping the of sub-schema (e.g. { type: "string", format: "url" }) from every scalar-array validation entry before handing it to buildYup() (schema-to-yup). schema-to-yup's array builder already fully supports this shape and recursively validates each item — it just never received it.
• The fix is two lines: re-attach of in both branches of the transform. This is generic, not "Tools"-specific — any scalar-array field the backend's validation array marks with of (Investigations, publicationAboutDataset, syntheticDataWebLink, etc.) is now validated the same way.
• Extracted generateValidationRules out of CreateDataset.tsx into src/utils/formHydration.tsx (alongside its sibling pure helpers) so it has a real unit test instead of being untested inline logic — which is what let this bug ship unnoticed in the first place.

Why it works: schema-to-yup's YupArray.itemsOf() (node_modules/schema-to-yup/src/types/array/array.js) reads this.constraints.of and recursively builds a per-item Yup validator from it — including format: "url" → .url(). The transform function just needed to stop deleting that key before yup ever saw it.

Issue ticket link

https://hdruk.atlassian.net/browse/GAT-9237

Checklist before requesting a review

• I have performed a self-review of my code
• I have added appropriate unit tests
• I have created mocks for unit tests (where appropriate) — n/a, no new HTTP/data mocking needed
• The interface is responsive (where appropriate) — n/a, no UI change (reverts to the existing standard form error display)
• The interface is at least AA (where appropriate) — n/a, no UI change

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