Separate into 4 modules * init_instance: load the cubicweb repository from the `pyramid_cubicweb.instance` configuration key * defaults: provides cw-like defaults for the authentication and session management * core: make cubicweb use the authentication and session management of pyramid. It assumes the application provides the auth policies and session factory, and that the `cubicweb.*` registry entries are correctly initialised. This is this only required module or pyramid_cubicweb, the other ones are optional if the application provides its own versions of what they do. * bwcompat: provides a catchall route that delegate the request handling to an old-fashion cubicweb publisher (ie using url_resolver and controllers). Related to #4291173