Remove unused _PyArg_VaParseTupleAndKeywordsFast() #107196
Description
It seems like the _PyArg_VaParseTupleAndKeywordsFast() function is no longer used in the Python code base.
Moreover, Argument Clinic (Tools/clinic/clinic.py) can produce code calling the _PyArg_ParseTupleAndKeywordsFast() function, but it is not the case currently: _PyArg_ParseStackAndKeywords() is used instead.
What's the status of these two functions, _PyArg_ParseStackAndKeywords() and _PyArg_VaParseTupleAndKeywordsFast()?
cc @erlend-aasland @serhiy-storchaka