Barycentric evaluation

[Sword-Smith]

For a faster recursive verifier, we need to implement "barycentric evaluation". Here's Rust code for that:

    pub fn barycentric_evaluate(
        codeword: &[XFieldElement],
        indeterminate: XFieldElement,
    ) -> XFieldElement {
        let root_order = codeword.len().try_into().unwrap();
        let generator = BFieldElement::primitive_root_of_unity(root_order).unwrap();
        let mut numerator = xfe!(0);
        let mut denominator = xfe!(0);
        let mut domain_iter_elem = bfe!(1);
        for code_word_elem in codeword {
            let domain_shift_elem = indeterminate - domain_iter_elem;
            let domain_over_domain_shift_elem = domain_iter_elem.lift() / domain_shift_elem;
            numerator += domain_over_domain_shift_elem * *code_word_elem;
            denominator += domain_over_domain_shift_elem;
            domain_iter_elem *= generator;
        }

        numerator / denominator
    }

See (https://github.com/TritonVM/triton-vm/pull/266) for context.