Add setup scripts to `systemPackages` & VM testing environments to `packages`

[eureka-cpu]

• Closes #9 Adds all previous scripts from the DO box /app/bin to common.nix to be shared between lasr_node virtual machines. This all gets bundled into a new global script, setup-working-dir.sh, which handles initializing everything that is expected to be in the /app directory and is part of #10
• Closes #10 Starts lasr_node on server launch
• Closes #12 Pulls docker images declaratively, making them available to the guest machine on boot
• Closes #13 Uses the oci-runtime to run the pre-pulled docker images from #12 in an on server launch
• Closes #15 Adds documentation for using nix-darwin and general MacOS setup
• Closes #16 Adds a new global script init-env.sh for persisting environment variables between boots, this is also part of #10
• Closes #19 Adds a local VM image for local development of lasr_node deployments for all supported systems.
• Closes #20 Adds a CI check for the new local VM images.

[eureka-cpu]

Super clean initialization set-up, three commands total and you have yourself a lasr_node hosted on a Nix VM. Very impressive! I see there may be some connectivity issues once inside the VM. This PR has a lot in it so far, so is that something you're wanting to handle in a separate PR?

Yeah this PR was just my development branch to get things to the point they could be further iterated on.