fix ``call_service`` API and add test service API
``call_service`` was taking a session argument. But Service is an AppoObject and
already has the same session accessible as ``self._cw``.
[devtool-testlib] add deprecated entry point for publish method
6c2119509fac renamed ``publish`` to ``handle_request``. And removed the older testlib
function (because the semantic of handle_request is quite different from the
publish one). However it seems to do more harm that good and I'm adding proxy with
deprecation warning for those.