sage.categories: Replace import of ZZ by py_scalar_parent(int)

[mkoeppe]

This is so that we can apply the category system to other numerical towers.

This can be tested with #29874, #29875.

Depends on #29873

CC: @tscrim @videlec

Component: refactoring

Keywords: sd111

Issue created by migration from https://trac.sagemath.org/ticket/29877

[mkoeppe]

Dependencies: #29873

[mkoeppe]

Changed keywords from none to sd111

[mkoeppe]

comment:4

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