Enable build of systemd-oomd and ship it in a systemd-oomd package

sd-oomd makes use of cgroups v2 (that is now enabled in bookworm) to kill processes in certain cgroups early (if it is enable for those cgroups), before the kernel's OOM killer needs to kick in. This can make the user interface more responsive and avoid clogging during high load use cases. Modern desktop environments like GNOME or KDE have pretty good integration for this already.

I propose to ship the same default configuration as has been used in Fedora for a while already. Shipping sd-oomd via an individual systemd-oomd package allows any user (or desktop environment) to install/depend on this package optionally, if they want to use/enable OOMD.