bpo-46541: Discover the global strings. (gh-31346)

Instead of manually enumerating the global strings in generate_global_objects.py, we extrapolate the list from usage of _Py_ID() and _Py_STR() in the source files.

This is partly inspired by gh-31261.

https://bugs.python.org/issue46541

Objects/typeobject.c

@@ -4546,6 +4546,7 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
             Py_DECREF(sorted_methods);
             return NULL;
         }
+        _Py_DECLARE_STR(comma_sep, ", ");
         joined = PyUnicode_Join(&_Py_STR(comma_sep), sorted_methods);
         method_count = PyObject_Length(sorted_methods);
         Py_DECREF(sorted_methods);