PyArg_ParseTupleAndKeywords(), _PyArg_ParseTupleAndKeywordsFast() and like.

Issue #29289. Convert methods:

* fromkeys() class method
* setdefault()
* popitem()
* move_to_end()

Issue #29286. Run Argument Clinic to get the new faster METH_FASTCALL calling
convention for functions using "boring" positional arguments.

Manually fix _elementtree: _elementtree_XMLParser_doctype() must remain
consistent with the clinic code.

Issue #29286. Use METH_FASTCALL calling convention instead of METH_VARARGS to
parse "boring" position arguments. METH_FASTCALL is faster since it avoids the
creation of a temporary tuple to pass positional arguments.

Replace PyArg_UnpackTuple() with _PyArg_UnpackStack()+_PyArg_NoStackKeywords().

Issue #29286.

Issue #29286. Run Argument Clinic to get the new faster METH_FASTCALL calling
convention for functions using only positional arguments.

Issue #29286. Use METH_FASTCALL calling convention instead of METH_VARARGS to
parse position arguments. METH_FASTCALL is faster since it avoids the creation
of a temporary tuple to pass positional arguments.

Issue #29286. Change _PyStack_UnpackDict() prototype to be able to notify of
failure when args is NULL.

Issue #29286. Similar to _PyArg_NoKeywords(), but expects a tuple of keyword
names, instead of a dict.

Issue #29286. Function similar to PyArg_ParseTuple(), but uses a C array of
PyObject* to pass arguments. Don't support the compatibility mode.

Issue #29286.

Issue #29029. Patch written by Serhiy Storchaka.

Factorize argument checks in:

* vgetargskeywordsfast()
* vgetargskeywordsfast_impl()

Issue #29259: Write fast path in _PyCFunction_FastCallKeywords() for
METH_FASTCALL, avoid the creation of a temporary dictionary for keyword
arguments.

Cleanup also _PyCFunction_FastCallDict():

* Don't dereference func before checking that it's not NULL
* Move code to raise the "no keyword argument" exception into a new
  no_keyword_error label.

Update python-gdb.py for the change.

Changed stack layout bit for "easy to explain."

Thanks to Evan_ for the report and patch.