Message 344577 - Python tracker

Now that PEP 590 has been implemented, a lot of old code can be cleaned up. In particular:

- get rid of _PyMethodDef_RawFastCallXXX() functions and replace them by vectorcall functions for each calling convention
- get rid of FastCallDict() implementations for specific types, but keep the generic _PyObject_FastCallDict()
- get rid of some specific tp_call implementations: try to use tp_call=PyVectorcall_Call in more places