tools/python: change 's#' size type for Python >= 3.10

tools/python: change 's#' size type for Python >= 3.10

Python < 3.10 by default uses 'int' type for data+size string types
(s#), unless PY_SSIZE_T_CLEAN is defined - in which case it uses
Py_ssize_t. The former behavior was removed in Python 3.10 and now it's
required to define PY_SSIZE_T_CLEAN before including Python.h, and using
Py_ssize_t for the length argument. The PY_SSIZE_T_CLEAN behavior is
supported since Python 2.5.

Adjust bindings accordingly.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>