Replace current CI implementation with Nix-flake based CI

[notgne2]

Description

We have newer practices for CI systems, so we should probably utilize them here, including our newest addition: mkPipeline, which generates individual pipeline steps for CI out of your flake, as opposed to lumping them all into a nix flake check step.

Related issue(s)

#26

✅ Checklist for your Pull Request

Related changes (conditional)

• Tests

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from
    silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • README
    • Haddock

Stylistic guide (mandatory)

• My commits comply with the policy used in Serokell.
• My code complies with the style guide.

[notgne2]

(might take some messing around with, this is my first time setting something up with mkPipeline)

[notgne2]

that seems to all be working except for weeder, which fails with

weeder: user error (Didn't find exactly 1 cabal file in .)

I might leave figuring that out to somebody that knows more about cabal

[notgne2]

Setting as draft until serokell/serokell.nix#69 is addressed, then will need to clean up commits

[dcastro]

I noticed that we're missing a few steps we used to have (there may be more):

• golden tests
• validate cabal files
• stylish
• lint (there is a new hlilnt step now, but looking at the logs it doesn't seem like it's actually running hlint)
• shellcheck
• linux static executable
• xrefcheck

Also:

• the tests step seems to be building the tests component, but not actually running it
• same for the haddock step
• same for the doctests step (In fact, I had issues trying to get doctests to run correctly on the CI before. So if we can't get it to run and pass, we might as well just ignore it in the CI, which is what we've been doing so far).

Questions:

• How do I run these CI steps locally? Previously, I was able to copy/paste the commands from .buildkite/pipeline.yml. But I'm not familiar with flakes, so I wouldn't know how to reproduce this locally.

[notgne2]

I'll add in the missing test-runnig and try to add all the missing tests too

How do I run these CI steps locally?

With using mkPipeline, it's generating our pipeline steps from what is under packages and checks, the same things that will be built by Nix if you run nix flake check.

[notgne2]

Adding xrefcheck would be ugly unless we can first deal with serokell/xrefcheck#54 (which would probably ending up looking exactly like this PR)

[notgne2]

It also seems like "validate cabal files" might be tedious to add, I tried it and it failed while attempting network access, is this because I configured it wrong? or is that step just impure

[dcastro]

It also seems like "validate cabal files" might be tedious to add, I tried it and it failed while attempting network access, is this because I configured it wrong? or is that step just impure

Looks like it's impure. The script validate-cabal-files.sh calls stack2cabal, which I think needs to fetch the stack resolver.