Replacement of AJV by Valibot

We did some work to test DCAR performance using several different parsing libraries: AJV, Valibot, Zod & Zod Mini. The result of our testing can be found on this [document](https://docs.google.com/document/d/1z5BKp9m9sLwvqZt-4_R_KKWXk1sGP9YiztB-nqY3PcI/edit?tab=t.0#heading=h.npptotnavayf)

The github issue for that work can be found https://github.com/guardian/dotcom-rendering/issues/14548

We now want to replace AJV by Valibot and check the actual performance result in production. We would most probably want to do this behind a switch, so that we can quickly revert back to AJV if the performance goes down more than what we expected