languages/haskell.nix: address PR comments

- Rename hls -> haskell-language-server to match the nixpkgs name
- Remove unneeded injection
- Only set lsp filetypes in the language module, not the preset
- Remove unneeded `mkDefault`
- Use `root_markers` instead of yucky inline Lua

modules/plugins/lsp/presets/haskell-language-server.nix

@@ -0,0 +1,30 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: let
+  inherit (lib.meta) getExe';
+  inherit (lib.modules) mkIf;
+  inherit (lib.nvim.types) mkLspPresetEnableOption;
+
+  cfg = config.vim.lsp.presets.haskell-language-server;
+in {
+  options.vim.lsp.presets.haskell-language-server = {
+    enable = mkLspPresetEnableOption "haskell-language-server" "Haskell" [];
+  };
+
+  config = mkIf cfg.enable {
+    vim.lsp.servers.haskell-language-server = {
+      enable = true;
+      cmd = [(getExe' pkgs.haskellPackages.haskell-language-server "haskell-language-server-wrapper") "--lsp"];
+      root_markers = ["hie.yaml" "stack.yaml" "cabal.project" "*.cabal" "package.yaml"];
+      settings = {
+        haskell = {
+          formattingProvider = "ormolu";
+          cabalFormattingProvider = "cabal-fmt";
+        };
+      };
+    };
+  };
+}