bump(sys-apps/baselayout): Updates for systemd
chore(systemd): remove gentoo-systemd-integration from systemd build
chore(sys-apps/systemd): Remove old version
chore(sys-apps/systemd): sync/cleanup systemd ebuilds.

Pull in some updates from upstream Gentoo.
As a follow up to the gentoo-systemd-integration removal prune the now
unused vanilla use flag and our custom openrc use flag along with it.
fix(sys-apps/systemd): Add tmpfiles rule for resolv.conf

This path has changed after v213 so it must be handled here instead of
baselayout now.
Merge pull request #679 from marineam/systemd

Systemd maintnance