Although this is a refactor for normal users of Doom, it is a bugfix for
one (I assume) unsupported configuration: when Doom is not running from
a git checkout. In that case, `doom--help-package-configs` currently
returns Git's error messages. This breaks `doom/help-packages` because
it expects each returned line to contain at least one `:` character, so
it errors out with `Wrong number of arguments: (file line _match &rest),
2`.
Using ripgrep here should be equivalent for normal users as long as they
have not added untracked files not covered by Doom's .gitignore.
e203309e5c