(WIPonWIP) Remove Distrobox & migrate to zst instead of local registry

[raven0034]

I should start a garage if I get any more whips. Anyway, cars... speed! A local FNG container capable of login times as low as sub-6 seconds is in your area!

As per #14 , removed Distrobox, cutting a significant amount of overhead with container startup times, as well as allowing for initial progress to be made on isolating the container as much as reasonably possible & integrating more on a "as needed" basis rather than trying to integrate basically the entire host.

Also changed over from using a local registry to using podman save to send it to a zst archive, which each machine will decompress and skopeo copy (faster than podman load) locally and run. Produced compressed image is ~1.5GB and copy is bottlenecked by connection speed - gigabit --> expected to take just shy of 15 seconds.

Once image is present on any given machine, subsequent logins now take sub-10 seconds consistently, with a lowest 5.9s clocked yesterday.

Main known issue is a couple of default keybinds being borked.

See documentation in changed files for explanation of new setup.

Remaining TODOs largely as in #14 and any docs added here.

[raven0034]

Noted issue: Halatro via dcspkg relies on /run/host/modules - /run/host was a Distrobox mount. Can mount /modules alternatively, best to check conditionally for dev purposes.

[raven0034]

Couple of other bits being flaky e.g. Sober to do with diffs in caps (works on the other branch when dropping gl thread opts - to be committed; privileged inherits all caps from host; all caps is not what I'm going for here). Edit: Sober issue not caps related.

Also experimenting around with systemd unit, which has fixed key bind issues in testing.

[raven0034]

Successful test this evening, will be doing a bit of clean-up and am currently in the process of writing a fair chunk of docs, then should be good to come out of draft :)

Mission success so far though!