This implements a crude mechanism for signalling my router to add the
packets to its own qdisc.
The way in which this is implemented with nftables is hacky because of
NixOS’ limitations on build-time checking (which obviously can’t know
about the existence of cgroups on the target).
I renewed the thermal paste on its GPU and replaced the stock fan with
two Noctua NF-A9 PWM that are controlled via the mainboard’s fan headers
(connected via a Y splitter), so corectrl is no longer necessary.