Added additional operators single_ and append_ to operations on Lists

[TimSheard]

Added file ListSplit.hs which introduces data ListSplit and combine functions Added a ListSplit component to ListSpec Added cases to propagateSpec, toPreds, conformsTo, genFromTypeSpec Added a bunch of tests and examplea

Description

Checklist

• [x] Commit sequence broadly makes sense and commits have useful messages
• [x] New tests are added if needed and existing tests are updated
• [ ] 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)
• [ ] 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)
• [x] Code is formatted with fourmolu (use scripts/fourmolize.sh)
• [x] Cabal files are formatted (use scripts/cabal-format.sh)
• [x] hie.yaml has been updated (use scripts/gen-hie.sh)
• [x] Self-reviewed the diff

[MaximilianAlgehed]

I suggest you add appendFn and singleFn to the arbitrary instance for TestableFn fn in Constrained.Properties to make sure that the propagateFun implementaitons are correct.