bookmark: use `list_paths` to access path definition
The content of the `[paths]` config section is receiving transformation that
make it hard to recognise whats the actual name, and the next changeset will
make it worse. So we use the official API for this instead.
Differential Revision: https://phab.mercurial-scm.org/D10448
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}