Replace PyObject_CallFunctionObjArgs() with fastcall

* PyObject_CallFunctionObjArgs(func, NULL) => _PyObject_CallNoArg(func)
* PyObject_CallFunctionObjArgs(func, arg, NULL) => _PyObject_CallArg1(func, arg)

PyObject_CallFunctionObjArgs() allocates 40 bytes on the C stack and requires
extra work to "parse" C arguments to build a C array of PyObject*.

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

This change is part of the fastcall project. The change on listsort() is
related to the issue #23507.

Modules/_struct.c

@@ -2046,7 +2046,7 @@ cache_struct(PyObject *fmt)
         return s_object;
     }
 
-    s_object = PyObject_CallFunctionObjArgs((PyObject *)(&PyStructType), fmt, NULL);
+    s_object = _PyObject_CallArg1((PyObject *)(&PyStructType), fmt);
     if (s_object != NULL) {
         if (PyDict_Size(cache) >= MAXCACHE)
             PyDict_Clear(cache);