split up repo

[arcnmx]

Rationale:

• modules should not be in this repo because any changes to them must be copied into the built system, which is silly and unnecessary
  • consider how this interacts with modules that also depend on packages defined in this repo?
• lib would be nice to have in a smaller common repo
• flakes will make it easier to have dependencies without making everyone feel awful
• base16 could be a repo of its own, and probably so could a bunch of other stuff too

Consider (automatically) splitting up package repos into one flake per package even, and deploying them as orphan branches/tags?

(this is kind of very slowly happening)