[config] fix the load_site_cubicweb() method for to 'new-style' cubes (closes #16059402) We first try to load the site_cubicweb module from the cubicweb_<cube> package, and if it fails, revert back to old cube path.

.. _rset_module:

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

.. automodule:: cubicweb.rset

    .. autoclass:: ResultSet
        :members: