horner evaluations and polynomial representation

i think the utils::horner_evaluate function is useless because we can see that univariate::DensePolynomial uses the Horner evaluation in ark-poly@0.4.2 which uses Self::horner_evaluate in both parallel and non-parallel features.

however, as far as i understand the current state of the code of FRI, this would require switching the polynomial reprensentation from raw coefficients to true polynomials.