bpo-32030: Don't call _PyPathConfig_Fini() in Py_FinalizeEx() (#4667)

Changes:

* _PyPathConfig_Fini() cannot be called in Py_FinalizeEx().
  Py_Initialize() and Py_Finalize() can be called multiple times, but
  it must not "forget" parameters set by Py_SetProgramName(),
  Py_SetPath() or Py_SetPythonHome(), whereas _PyPathConfig_Fini()
  clear all these parameters.
* config_get_program_name() and calculate_program_full_path() now
  also decode paths using Py_DecodeLocale() to use the
  surrogateescape error handler, rather than decoding using
  mbstowcs() which is strict.
* Change _Py_CheckPython3() prototype: () => (void)
* Truncate a few lines which were too long