templater: wrap get/min/max result so map operation can apply to element
See the test for usage example.
wraphybridvalue() takes a key/value pair because a hybrid dict passes a key
to its makemap() function. Since makemap() of showmanifest() doesn't need
a key, it's set to None.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}