We add _sympy_ methods to matrix and vector classes, converting to sympy.matrices.Matrix.

https://docs.sympy.org/latest/modules/matrices/matrices.html

CC: @kcrisman @videlec @tscrim

Component: symbolics

Author: Matthias Koeppe

Branch/Commit: c365f18

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/31942