We add a method multivariate_interpolation to the MPolynomialRing_base class.

Given a bound on the degree and either point/value pairs or a function, it returns the respective interpolation polynomial.

CC: @schmittj @videlec

Component: algebra

Keywords: interpolation, polynomials

Author: Johann Birnick

Branch/Commit: 7eea889

Reviewer: Johannes Schmitt, Lorenz Panny

Issue created by migration from https://trac.sagemath.org/ticket/34651