bpo-41909: Enable previously disabled recursion checks. (GH-22536)

Enable recursion checks which were disabled when get __bases__ of
non-type objects in issubclass() and isinstance() and when intern
strings. It fixes a stack overflow when getting __bases__ leads
to infinite recursion.

Originally recursion checks was disabled for PyDict_GetItem() which
silences all errors including the one raised in case of detected
recursion and can return incorrect result. But now the code uses
PyDict_GetItemWithError() and PyDict_SetDefault() instead.

Objects/unicodeobject.c

@@ -15734,9 +15734,7 @@ PyUnicode_InternInPlace(PyObject **p)
     }
 
     PyObject *t;
-    Py_ALLOW_RECURSION
     t = PyDict_SetDefault(interned, s, s);
-    Py_END_ALLOW_RECURSION
 
     if (t == NULL) {
         PyErr_Clear();