bpo-3605, bpo-38733: Optimize _PyErr_Occurred(): remove "tstate ==
NULL" test.
Py_FatalError() no longer calls PyErr_Occurred() if called without
holding the GIL. So PyErr_Occurred() no longer has to support
tstate==NULL case.
_Py_CheckFunctionResult(): use directly _PyErr_Occurred() to avoid
explicit "!= NULL" test.
* Replace global var Py_VerboseFlag with interp->config.verbose.
* Add _PyErr_NoMemory(tstate) function.
* Add tstate parameter to _PyEval_SetCoroutineOriginTrackingDepth()
and move the function to the internal API.
* Replace _PySys_InitMain(runtime, interp)
with _PySys_InitMain(runtime, tstate).