[tox] Update doc testenv to account for documentation restructuring * Build doc from `doc` directory. * Use `sphinx-build` directly instead of `make` as this now works and allows to build within .tox temporary environment (instead of doc/_build), preferable for a "test" action. Related to #5447161.

.. _rset_module:

:mod:`cubicweb.rset`
====================

.. automodule:: cubicweb.rset

    .. autoclass:: ResultSet
        :members: