(Merge 3.4) Issue #23571: Enhance Py_FatalError()

* Display the current Python stack if an exception was raised but the exception
  has no traceback
* Disable faulthandler if an exception was raised (before it was only disabled
  if no exception was raised)
* To display the current Python stack, call PyGILState_GetThisThreadState()
  which works even if the GIL was released