Drop haskell-tree-sitter in favor of custom bindings to tree-sitter.
haskell-tree-sitter is outdated and seems unmaintained.

The implementation add low-level bindings to tree-sitter and traverses
the AST in Haskell.

We suspect that many FFI calls are more expensive than performing just a
single API call to a C function that does the traversal.

This will be addressed in upcoming commits.

@prerequisite-for add-languages-elm-shell-nix

Regresses in that we only support Haskell for now, as Elm, Nix or Bash
are not available as tree-sitter-* Haskell packages.