Adding version 2 of the SDW CI scripts

[mig5]

Closes #39

Works towards https://github.com/freedomofpress/infrastructure/issues/4603

Relates to https://github.com/freedomofpress/infrastructure/pull/4659

This is all the code currently in use on the new version of the CI.

The docs are updated, but I am yet to do a new diagram.

[eloquence]

Per infra team meeting, took a quick spin through the docs portion only. Since I've not performed a code review, not submitting a formal +1, but docs look good with a couple of comments/questions.

[mig5]

There is some bug with my automatic update + snapshot logic that runs nightly. It is not iterating over both VMs for the same version, it's updating the first machine but not the second. I'll look into it.

[mig5]

Finally fixed what was indeed a bug in the nightly self-update/snapshot system, affecting the 'second' VM for whatever version.

I feel like this PR could be merged now, though of course, no-one's reviewed the code.. who wants to do that? Someone who was familiar with the original flow?

From a 'how does the build/test work' perspective, it's more or less the same as it ever was with the runner.py (which is merely simplified now to have no teardown logic). The rest of the 'new' stuff is mostly the run.py which runs on the bastion to restore/power up VMs to perform that runner.py in the dom0 once booted.

[legoktm]

Just a small review since you asked for one :)

[mig5]

The sd-dev VM is now Debian (11 on Qubes 4.1, 12 on Qubes 4.2) with podman instead of docker.

The config/sd-journalist files are now copied from the cloned repo, in sd-dev, rather than downloaded.

I also added Slack notifications, just for if the CI fails (not sending notifications on success, to avoid alert fatigue).

I think we should be ok to merge this in now (as discussed in infra sync, I'll probably self-merge, but I'll wait another 12 hours or so in case Kunal spots any other issues).

[legoktm]

LGTM! Thanks so much for working on this :)