templater: use template context to render old-style list template
Prepares for dropping the 'templ' resource.
This means old-style list templates are processed by the same engine class
as the one for the list node. I think that's fine since templates for the
same list should be tightly coupled, and I believe the extension point for
the engine classes isn't actually used.
Now templatekw._showlist() is a compatibility wrapper for _showcompatlist(),
and will be deprecated soon. The function is still marked as private since
I plan to change the interface to get rid of closures capturing context and
mapping.
{header}
<title>Error</title>
<description>Error</description>
<item>
<title>Error</title>
<description>{error|escape}</description>
<guid>https://mercurial-scm.org/#error</guid>
</item>
</channel>
</rss>