Upgrade to GHC-9.4 resulting in lower compile-time memory usage

[basvandijk]

Building ic-hs with GHC-9.0 requires ~13GB of memory. Upgrading to GHC-9.4 reduces this by around 30% to ~9GB:

[mraszyk]

LGTM

[ggreif]

This is nice, but we need a coherent plan how to promote such changes downstream. E.g. dfinity/motoko will need the same GHC so that we can reuse the binary cache artefacts. Hopefully nix will take care of this.

[nomeata]

I thought dfinity/motoko imports this repo as a whole, so for ic-ref-test it uses the same nixpkgs pin and thus the cache can be shared?

[ggreif]

Hopefully. But we also have a majority of M1 Macs in the meantime which have to build locally. So that is one difference.