core/packs/pack-files: Enable recentf mode

Renamed from pack-dired, and enable recentf.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
core/packs/pack-files: Diminish dired-omit-mode

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>