Factorize code in Polynomials and Ore Polynomials

[xcaruso]

After #29629, we propose to make the class Polynomial inherit from the abstract class SkewPolynomial (since a lot of codes is shared between these two classes and a normal polynomial is just a skew polynomial under the identity map).

Any comment?

CC: @tscrim

Component: algebra

Issue created by migration from https://trac.sagemath.org/ticket/30054

[mkoeppe]

comment:3

Setting new milestone based on a cursory review of ticket status, priority, and last modification date.