fn to_limbs_field_vec<E: From<F>, F: Field>(x: &BigUint) -> Vec<E> {
        Self::to_limbs(x)
            .into_iter()
            .map(|x| F::from_canonical_u8(x).into())
            .collect::<Vec<_>>()
    }
Convert a BigUint to a Vec of F limbs (with len NB_LIMBS).
crates/core/machine/src/operations/field/params.rs