... using the method .domain() instead

This is preparation for #31894 - when _domain is a Cython attribute, it will not be directly accessible from Python.

Depends on #32112
Depends on #30473

CC: @mjungmath @egourgoulhon @vbraun

Component: manifolds

Author: Matthias Koeppe

Branch/Commit: u/mkoeppe/eliminate_direct_use_of_the_chart__domain_attribute @ bf62543

Reviewer: Travis Scrimshaw, Eric Gourgoulhon

Issue created by migration from https://trac.sagemath.org/ticket/32009