BUG: _cython_table bug fix
#21224 introduced a bug, where the ``conftest._cython_table`` isn't sorted by the function's name, but by the functions class name (i.e. "function"). This can make the sorting indeterministic and make the build fail on Python 2.7 and 3.5 at times.

This PR makes the sort order follow the functions names again and therefore be deterministic.