Cardano Updates

The -env jobs previously used recursive-nix to run `nix print-dev-env`
inside a derivation, but this fails on remote builders with:
  "recursive-nix is not supported yet by external derivation builders"

This commit replaces that approach with Import From Derivation (IFD):
- Read the mkShell output directly at evaluation time via builtins.readFile
- Filter out the self-referencing $out variable to break circular deps
- Embed the environment content directly in the wrapper script

The mkShell output already contains "declare -x VAR=value" lines which
is exactly what's needed. This approach:
- Avoids the recursive-nix requirement entirely
- Still includes all runtime dependencies (GHC, cabal, tools, etc.)
- Works on remote builders without special configuration

Both JS and Windows cross-compilation builds use head.hackage which
has a stale hash in the current haskell.nix. Filter both from
hydraJobs until upstream fixes the issue.

Switch from nixpkgs-2505 to nixpkgs-2511, updating haskell.nix
and all related inputs to their latest versions.