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/Objects/structseq.c b/Objects/structseq.c
index e4a4b45..db4aebe 100644
--- a/Objects/structseq.c
+++ b/Objects/structseq.c
@@ -9,11 +9,11 @@
 
 #include "Python.h"
 #include "pycore_dict.h"          // _PyDict_Pop()
-#include "pycore_tuple.h"         // _PyTuple_FromArray()
+#include "pycore_initconfig.h"    // _PyStatus_OK()
+#include "pycore_modsupport.h"    // _PyArg_NoPositional()
 #include "pycore_object.h"        // _PyObject_GC_TRACK()
-
 #include "pycore_structseq.h"     // PyStructSequence_InitType()
-#include "pycore_initconfig.h"    // _PyStatus_OK()
+#include "pycore_tuple.h"         // _PyTuple_FromArray()
 
 static const char visible_length_key[] = "n_sequence_fields";
 static const char real_length_key[] = "n_fields";