[dbapi] explicitly use the DBAPI version of CubicwebRequestBase As we plan to use a ConnectionCubicwebRequestBase by default we better have the dbapi explicitly asking for a DBAPI implementation.

[web/application] drop unused import unused since 3c85e734ce00

[web/test] properly reset the request connection related attribute A new request does not have those attribute to None. There have special value that we now properly reinstall.

[web/test] drop two undocumented suspicious regression test Those two test are not documented and use the API in the wrong way. They do not raise exception by chance. the current request signature is:: def request(self, rollbackfirst=False, url=None, headers={}, **kwargs): So the RQL have nothing to do here.

[webrequest] introduce an alternative implementation using the repoapi DBAPI specific parts of ``CubicWebRequestBase`` are extracted in a ``DBAPICubicWebRequestBase`` decicated class and a new ``ConnectionCubicWebRequestBase`` is introduced that provide the same services but using a repoapi.ClientConnection as data source. For now the ``DBAPICubicWebRequestBase`` is still used by default.

[repoapi] add an anonymous_cnx function This function return an anonymous ClientConnection. It aims to replace ``dbapi.anonymous_session``.

[repoapi] add a connect function This function takes a repo and authentication information to open a new Session and return a ClientConnection associated to it.

[client-connection] add an auto-close property for ClientConnection The next commit introduce a connect function that open a new Session and return an associated ClientConnection. The Session should not be used by anything else than the created ClientConnection, so we want to close it at the same time than the ClientConnection. The implementation in this changeset is simplistic. We probably want to move this notion in the session itself. This be improved once we have server side Connection

[cwuser] make CWUser callable, returning self for dbapi compatibility In the dbapi, Connection and Session have a ``user`` method to generated a user for a request In the repo api, Connection and Session have a user attribute inherited from SessionRequestBase prototype. This ugly hack allows to not break user of the user method. To ease transition from dbapi to repoapi we need the ClientConnection to be as compatible as possible with the dbapi. Adding this method goes in this direction. It'll get deprecated in the deprecation wave that will conclude the repoapi refactoring. related to #2503918

[client-connect] drop rqlst on rset returned client side The DBAPI used to drop the RQL syntax tree on rset to save bandwidth. We could stop doing it for In-memory client connection. However keeping the syntax tree leads to multiple tests failures. So we keep dropping it as the DBAPI always did. related to #2503918