Disable systemd-resolved

Previously, systemd-resolved was installed, but not used.

Starting with systemd-resolved-249.11-1.fc35.x86_64, this changed due to
this change:

> Create /etc/resolv.conf symlink if nothing is present yet (#2032085)

More context in: https://bugzilla.redhat.com/show_bug.cgi?id=2032085

Before this version, resolv.conf was a regular file managed by
NetworkManager.

This commit restores the previous behvaiour by disabling
systemd-resolved, removing /etc/resolv.conf if it is a symlink, and
restarting NetworkManager (so it creates a new resolv.conf).