Implement Haskell CI

[sjshuck]

From @andreasabel:

I notice though that CI does not cover all major GHC versions for mtl. I would recommend to add an autogenerated Haskell CI because this tests on different GHCs with their shipped libraries.
Haskell CI has to be build from the repo https://github.com/haskell-CI/haskell-ci (Hackage is too old and to seldom released), and you have to maintain the tested-with field in the cabal file. I also recommend to have a cabal.haskell-ci with content branches: master to avoid redundant CI runs.

[sjshuck]

@andreasabel What would you consider

all major GHC versions

to be?

[andreasabel]

Well, the constraint is base >= 4.12, so this means GHC 8.6 and up: 8.6.5 8.8.4 8.10.7 9.02 9.2.8 9.4.8 9.6.7 9.8.4 9.10.3 9.12.2 9.14.1

[meipp]

As of March 26 that would be ghc-9.12.4 instead of ghc-9.12.2

[meipp]

haskell-ci does not support MHS. I propose we have a generated haskell-ci.yml to test against all major GHC versions, and keep the current manually maintianed ci.yml for testing against MHS and for matrix testing ghc under windowx+linux+macos. We could remove a few ghc versions from the matrix test imho, now that all major versions will be tested by haskell-ci (using ubuntu-24.04 as of now).

opinions? @sjshuck
cc: @andreasabel

[sjshuck]

I'm sorry to say that my interest in implementing Haskell CI is low right now. They do not seem interested in making new Hackage releases, and getting set up with is unclear.

Our simple DIY CI solution seems good enough for now.

[sjshuck]

Thanks @hasufell for #182. This issue is moot now.