[3.14] gh-145376: Fix various reference leaks (GH-145377) (GH-145712)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Python/pythonrun.c

@@ -1151,6 +1151,7 @@ _PyErr_Display(PyObject *file, PyObject *unused, PyObject *value, PyObject *tb)
         "traceback",
         "_print_exception_bltin");
     if (print_exception_fn == NULL || !PyCallable_Check(print_exception_fn)) {
+        Py_XDECREF(print_exception_fn);
         goto fallback;
     }