... as previously done in #30022 for sage.rings.integer and sage.rings.rational.

This is to support modularization (#29705):

• in particular, for sagemath-categories (Modularization of sagelib: Break out separate packages sagemath-objects, sagemath-categories #29865), to make the functions py_scalar_parent and py_scalar_to_element (from sage.structure.coerce) fully functional without having to pull in PARI (at compile time or run time)
• likewise, for sagemath-polyhedra (Modularization of sagelib: Break out a separate package sagemath-polyhedra #32432) to support floating-point polyhedra and linear programming without having to pull in PARI (at compile time or run time).

CC: @kliem @videlec @tscrim @yyyyx4

Component: refactoring

Author: Matthias Koeppe, Jonathan Kliem

Branch/Commit: 629c319

Reviewer: Matthias Koeppe, Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/32701