Add cabal-gild and update hook

[palas]

Changelog

- description: |
    Added cabal-gild to dev shell, to haskell-style-lint hook script, and created CI action to check it.
  type:
    - maintenance

Context

We don't want to have to worry about the formatting of .cabal files, and we want it to be consistent. This PR tries to address this.

How to trust this PR

Probably check that the hook works for you. Also that you are happy with the changes and configuration, and that the CI passes.

I've also checked that it doesn't pass when the cabal file is modified and unformatted. See:

• Discarded commit: 8cbc6d7
• Failing action corresponding to the commit: Job 27020041405

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[carbolymer]

Blocking on misaligned comments in the cabal file.

Reason for block addressed