- new test case for pre-initialization of sys.warnoptions and sys._xoptions
- restored ability to call these APIs prior to Py_Initialize
- updated the docs for the affected APIs to make it clear they can be
  called before Py_Initialize
- also enhanced the existing embedding test cases
  to check for expected settings in the sys module
(cherry picked from commit bc77eff8)
Co-authored-by: Nick Coghlan <ncoghlan@gmail.com>