feat: Add bustd OOM killer to recommends

[mmstick]

When released, investigate worth of having this service as a recommends

[13r0ck]

I ran a test on a galp4 with 4GB of ram. Ran memtest 3000 and opened 20 visual studio code windows and waited until the system recovered.

Without Bustd: 44 seconds
With Bustd: 36 seconds

Which is great, but I am concerned that with bustd if I waited another 10 seconds the OS closed all VS code windows, without a warning, and provided no reason why. Then when trying to open VS code again all 20 windows would pop up again, and while trying to close them again, Bustd closed all of the windows again.
My feeling is that Bustd is too aggressive with closing processes.

[610th]

FYI: Ubuntu will add systemd-oomd in 22.04 LTS.

https://manpages.ubuntu.com/manpages/jammy/en/man8/systemd-oomd.8.html
https://lists.ubuntu.com/archives/ubuntu-devel/2022-January/041819.html

[XV-02]

@mmstick Given bustd's apparently over eager sensibilities, and the fact Ubuntu now supports systemd-oomd, do we wish to continue with this, rely on systemd-oomd, or what? What's our path forward?

[mmstick]

Is systemd-oomd any better?