STS tests based on constraints

[MaximilianAlgehed]

Description

This PR introduces the test setup for testing STS rules using the constraint library. It's a WIP effort but we have a running test for a simple STS rule: GOVCERT.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[lehins]

That's a good start with STS. Only minor changes are needed.

[MaximilianAlgehed]

@lehins I think this should be ready to merge

[TimSheard]

The goal of this PR is to prototype the use of the shrinking capabilities by testing that a rules maintain the constraints we used to generates a 'legitimate' state. We should add another rule, as suggested in the comments, where there are some real constraints. This way we get a better test of the capabilities.

Personally, I'd like to better understand how we shrink an environment using the constraints

[lehins]

👍 Thank you

[MaximilianAlgehed]

@TimSheard I think I've addressed your comments

[MaximilianAlgehed]

@lehins I added the POOL and DELEG rules here too. It might be worth while to merge this soon to avoid things changing beneath our feet.