gh-110964: Remove private _PyArg functions (#110966)

Move the following private functions and structures to
pycore_modsupport.h internal C API:

* _PyArg_BadArgument()
* _PyArg_CheckPositional()
* _PyArg_NoKeywords()
* _PyArg_NoPositional()
* _PyArg_ParseStack()
* _PyArg_ParseStackAndKeywords()
* _PyArg_Parser structure
* _PyArg_UnpackKeywords()
* _PyArg_UnpackKeywordsWithVararg()
* _PyArg_UnpackStack()
* _Py_ANY_VARARGS()

Changes:

* Python/getargs.h now includes pycore_modsupport.h to export
  functions.
* clinic.py now adds pycore_modsupport.h when one of these functions
  is used.
* Add pycore_modsupport.h includes when a C extension uses one of
  these functions.
* Define Py_BUILD_CORE_MODULE in C extensions which now include
  directly or indirectly (via code generated by Argument Clinic)
  pycore_modsupport.h:

  * _csv
  * _curses_panel
  * _dbm
  * _gdbm
  * _multiprocessing.posixshmem
  * _sqlite.row
  * _statistics
  * grp
  * resource
  * syslog

* _testcapi: bad_get() no longer uses METH_FASTCALL calling
  convention but METH_VARARGS. Replace _PyArg_UnpackStack() with
  PyArg_ParseTuple().
* _testcapi: add PYTESTCAPI_NEED_INTERNAL_API macro which is defined
  by _testcapi sub-modules which need the internal C API
  (pycore_modsupport.h): exceptions.c, float.c, vectorcall.c,
  watchers.c.
* Remove Include/cpython/modsupport.h header file.
  Include/modsupport.h no longer includes the removed header file.
* Fix mypy clinic.py

1 files changed, 3 insertions, 3 deletions

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index c6a8dda..577fea3 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -2023,10 +2023,10 @@ test_pythread_tss_key_state(PyObject *self, PyObject *args)
        return repr(self)
 */
 static PyObject*
-bad_get(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+bad_get(PyObject *module, PyObject *args)
 {
     PyObject *self, *obj, *cls;
-    if (!_PyArg_UnpackStack(args, nargs, "bad_get", 3, 3, &self, &obj, &cls)) {
+    if (!PyArg_ParseTuple(args, "OOO", &self, &obj, &cls)) {
         return NULL;
     }
 
@@ -3340,7 +3340,7 @@ static PyMethodDef TestMethods[] = {
     {"W_STOPCODE", py_w_stopcode, METH_VARARGS},
 #endif
     {"test_pythread_tss_key_state", test_pythread_tss_key_state, METH_VARARGS},
-    {"bad_get", _PyCFunction_CAST(bad_get), METH_FASTCALL},
+    {"bad_get", bad_get, METH_VARARGS},
 #ifdef Py_REF_DEBUG
     {"negative_refcount", negative_refcount, METH_NOARGS},
     {"decref_freed_object", decref_freed_object, METH_NOARGS},