phases: convert remote phase root to node while reading them
This is currently a bit silly as we will convert them back to node right after,
but that is an intermediate step before doing more disruptive changes.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}