utils: move finddirs() to pathutil This is a follow-up to c21aca51b392 (utils: move the `dirs` definition in pathutil (API), 2019-11-06). finddirs() is closely related to dirs and used by it. Differential Revision: https://phab.mercurial-scm.org/D7388

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    "arc.land.onto.default": "@",
    "base": "hg:.^"
}