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.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index dcd7b5e..81b6c48 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -1970,8 +1970,7 @@
         }
 
         for (i = 0; i < saved_ob_size ; i++) {
-            keys[i] = PyObject_CallFunctionObjArgs(keyfunc, saved_ob_item[i],
-                                                   NULL);
+            keys[i] = _PyObject_CallArg1(keyfunc, saved_ob_item[i]);
             if (keys[i] == NULL) {
                 for (i=i-1 ; i>=0 ; i--)
                     Py_DECREF(keys[i]);