pub fn extend(&mut self, other: &DenseMultilinearPolynomial<F>) {
        debug_assert_eq!(self.evals.len(), self.len);
        debug_assert_eq!(other.evals.len(), self.len);
        self.evals.extend(other.evals.iter().cloned());
        self.n_vars += 1;
        self.len *= 2;
        debug_assert_eq!(self.evals.len(), self.len);
    }
Extends this DenseMultilinearPolynomial by concatenating another polynomial of the same length.
crates/math/src/polynomial/dense_multilinear_poly.rs