chore: clean up unified tests

[euonymos]

Summary

The way tests were organized was very messy. No clean separation, use of higher monad than needed, and so on. The docs were updated accordingly in this PR

Type of Change

Please mark the relevant option(s) for your pull request:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring (improving code quality without changing its behavior)
• Documentation update (adding or updating documentation related to the project)

Checklist

Please ensure that your pull request meets the following criteria:

• I have read the Contributing Guide
• My code follows the project's coding style and best practices
• My code is appropriately commented and includes relevant documentation
• I have added tests to cover my changes
• All new and existing tests pass
• I have updated the documentation, if necessary

[sourabhxyz]

@euonymos Could you rebase it? Thanks!

[sourabhxyz]

Thanks @euonymos, PR LGTM.

[euonymos]

Ups I didn't check all tests, ok, let me do it now just to be sure. Also I think I dropped fourmolu somehow.