test/lazygit: add fish integration test

This does also add a test module for lazygit since there wasn't one
already

tests/modules/programs/lazygit/fish-integration-enabled.nix

@@ -0,0 +1,18 @@
+{ config, ... }:
+
+{
+  programs.fish.enable = true;
+
+  home.preferXdgDirectories = false;
+
+  programs.lazygit = {
+    enable = true;
+    shellWrapperName = "lg";
+    enableFishIntegration = true;
+  };
+
+  nmt.script = ''
+    assertFileContent home-files/.config/fish/functions/${config.programs.lazygit.shellWrapperName}.fish \
+      ${./fish-integration-expected.fish}
+  '';
+}