gh-105922: Use PyImport_AddModuleRef() function (#105999)

Replace PyImport_AddModuleObject() + Py_XNewRef() with
PyImport_AddModuleRef() to get directly a strong reference.

Author: vstinner

Python/import.c

@@ -1382,8 +1382,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         if (_PyUnicode_EqualToASCIIString(name, p->name)) {
             if (p->initfunc == NULL) {
                 /* Cannot re-init internal module ("sys" or "builtins") */
-                mod = PyImport_AddModuleObject(name);
-                return Py_XNewRef(mod);
+                return import_add_module(tstate, name);
             }
             mod = _PyImport_InitFunc_TrampolineCall(*p->initfunc);
             if (mod == NULL) {

Python/pythonrun.c

@@ -276,7 +276,7 @@ PyRun_InteractiveOneObjectEx(FILE *fp, PyObject *filename,
         return parse_res;
     }
 
-    PyObject *main_module = Py_XNewRef(PyImport_AddModuleObject(&_Py_ID(__main__)));
+    PyObject *main_module = PyImport_AddModuleRef("__main__");
     if (main_module == NULL) {
         _PyArena_Free(arena);
         return -1;