Spar Polysemy: Random effect

[isovector]

This PR minimizes the MonadIO footprint still in Spar, by creating an effect that can generate random things.

Checklist

• The PR Title explains the impact of the change.
• The PR description provides context as to why the change should occur and what the code contributes to that effect.
• A file with the changelog entry in one or more suitable sub-sections. The sub-sections are marked by directories inside changelog.d.

[fisx]

What about this one? https://hackage.haskell.org/package/polysemy-zoo-0.7.0.1/docs/Polysemy-Random.html

I think this is fine for now, but I don't know if I like the abstraction. I would have made a more datatype-oblivious effect and then written application logic that uses that, and implements the functions below.

The way it looks now, I have to pull in the effect for generating scim tokens when i only want bytes for something completely unrelated.

I suppose you did this because it's easy to do and revisit and understand later? I'm happy with keeping it as is, just checking :)

[isovector]

In general, I think application-level effects should be as specific as possible. There's not much value in writing a really abstract effect, just to immediately specialize it. I'd be sympathetic to the argument that maybe we should expose these as Input UUID, or something, but I'm not entirely sure what it would buy us.