packaging: make "mercurial.defaultrc" a key in package_data Before this patch, we had a `mercurial` key with a `defaultrc/*.rc` value. It seems more correct to have a `mercurial.defaultrc` key with a `*.rc` value since `mercurial.defaultrc` it became a pacakge in 1390bb81163e (help: get helptext/ data from `resources` module if available, 2019-12-12). Differential Revision: https://phab.mercurial-scm.org/D8856