templatekw: mark _showlist() as deprecated (API)
.. api::
``templatekw._showlist()`` is deprecated in favor of
``templateutil._showcompatlist()``, which takes ``context`` in place of
``templ``.
templater: drop 'templ' from resources dict
Partially resolves cycle, templ -> context -> templ. This will make it easier
to replace the resources dict with new immutable resource mapper interface.