packaging: include templates with their package as key in package_data
This is similar to an earlier patch in this series. It seems more
correct to use `mercurial.templates.coal` etc as keys in the
`package_data` dict now that those modules are packages.
Differential Revision: https://phab.mercurial-scm.org/D8858
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}