gh-110815: Support non-ASCII keyword names in PyArg_ParseTupleAndKeywords() (GH-110816)

It already mostly worked, except in the case when invalid keyword
argument with non-ASCII name was passed to function with non-ASCII
parameter names. Then it crashed in the debug mode.

Python/getargs.c

@@ -1729,7 +1729,7 @@ vgetargskeywords(PyObject *args, PyObject *kwargs, const char *format,
                 return cleanreturn(0, &freelist);
             }
             for (i = pos; i < len; i++) {
-                if (_PyUnicode_EqualToASCIIString(key, kwlist[i])) {
+                if (PyUnicode_EqualToUTF8(key, kwlist[i])) {
                     match = 1;
                     break;
                 }