Add Haskell Language Server check to CI

[palas]

This PR adds a check to the CI that ensures that it works with the developer shell as it is.

Changelog

- description: |
    Add CI check that ensures HLS works with developer shell
  type:
  - test

Context

Recently we had an issue with HLS not working because of a bug. We could have catched that if we had a test in the CI that ensured HLS worked. This PR aims to address this.

How to trust this PR

Check the workflow makes sense. But basically, I would just look at the CI's output.

Checklist

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

[smelc]

@carbolymer> right now the new check is not required so we can merge manually before this new check is finished.

Regarding the merge queue's behavior, the documentation says it waits for required checks to be satisfied. So not sure if it merges as soon as required checks are green, ignoring the others. I'd be surprised if it was the case.

[palas]

I'm fine with the version bump. This GHA however takes 20 minutes, which is too long of a wait for each PR to get merged.

I don't remember, can you confirm that each PR will wait for this new check to complete before merging?

It takes 4 min now on cache hit. And, it is my understanding, that it should hit cache as long as dependencies for the project don't change