* nixos/earlyoom: bring the module up to date
Removes deprecated option `ignoreOOMScoreAdjust`, introduces `killHook`
as a replacement for `notificationsCommand`, and adds an `extraArgs`
option for things not covered by the module.
* nixos/earlyoom: add nixos test
* nixos/earlyoom: add reportInterval
Allows setting the interval for logging a memory report. Defaults to
3600 following upstream
(https://github.com/rfjakob/earlyoom/blob/master/earlyoom.default#L5)
to avoid flooding logs.
* nixos/earlyoom: add free{Mem,Swap}KillThreshold
Fixes https://github.com/NixOS/nixpkgs/issues/83504
Since systemd 243, docs were already steering users towards using
`journal`:
eedaf7f322
systemd 246 will go one step further, it shows warnings for these units
during bootup, and will [automatically convert these occurences to
`journal`](f3dc6af20f):
> [ 6.955976] systemd[1]: /nix/store/hwyfgbwg804vmr92fxc1vkmqfq2k9s17-unit-display-manager.service/display-manager.service:27: Standard output type syslog is obsolete, automatically updating to journal. Please update│······················
your unit file, and consider removing the setting altogether.
So there's no point of keeping `syslog` here, and it's probably a better
idea to just not set it, due to:
> This setting defaults to the value set with DefaultStandardOutput= in
> systemd-system.conf(5), which defaults to journal.
