bpo-29778: Ensure python3.dll is loaded from correct locations when Python is embedded (GH-21297)

Also enables using debug build of `python3_d.dll`
Reference: CVE-2020-15523

Python/dynload_win.c

@@ -168,9 +168,7 @@ dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,
     char funcname[258], *import_python;
     const wchar_t *wpathname;
 
-#ifndef _DEBUG
     _Py_CheckPython3();
-#endif
 
     wpathname = _PyUnicode_AsUnicode(pathname);
     if (wpathname == NULL)