Is your feature request related to a problem? Please describe.

We now support GHC 9.6+ versions. That means we should be able to use GHC2021 in Cabal file.

The GHC2024 is available in GHC 9.10, but we can add the extensions manually to common stanza.
We already use LambdaCase and GADTs extensively and the new additions would fit the codebase nicely.

See the proposal (link) which documents the reasoning for inclusion.

Describe the solution you'd like

1. Use the GHC2021 language edition in Cabal file.
2. Add the additions from GHC2024 to the common stanza
3. Check if Fourmolu/HLint needs to be told about default extensions
4. Remove the now default extensions from LANGUAGE pramas in files.
5. Enjoy the modern Haskell. 😎

Describe alternatives you've considered

We could conservatively stay on our semi-GHC2021 using the common stanza, but that leads to noise both in the Cabal file and in individual Haskell files.

Additional context

• GHC2024 - ghc-proposals documentation
• GHC2021 - ghc-proposals documentation
• The GHC20XX process