widening: pass in matchers instead of patterns
This matches how it's done for the non-ellipsis case. The oldmatch is
not used yet, but it should be used eventually when widening no longer
resends manifests and files the client already has.
Differential Revision: https://phab.mercurial-scm.org/D7099
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}