Cardano Updates

These workflow files still exist on master with pull_request triggers.
Without overriding them in this branch, GitHub Actions runs the master
versions on PRs, causing spurious cancelled/failed checks.

Remove benchmarks from the Windows testing bundle — JuicyPixels ANN
pragmas crash iserv-proxy during cross-compilation and benchmarks
aren't useful on Windows.

Fix ghc-lib-parser overlay to apply via haskellPackages.override
instead of haskell.packageOverrides which wasn't reaching the
nixpkgs haskell package set used by dev shell tools (fourmolu).