cue modules: move stdlib to pkg/alpha.dagger.io

In preparation for Europa, we will vendor multiple CUE modules:

- `pkg/alpha.dagger.io`: legacy non-europa packages
- `pkg/dagger.io`: core Europa packages
- `pkg/universe.dagger.io`: Europa universe

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

pkg/alpha.dagger.io/docker/compose/tests/testdata/index.ts

@@ -0,0 +1,13 @@
+import express from "express";
+import { get } from "env-var";
+
+
+const app = express();
+
+const port: number = get('PORT').required().asPortNumber();
+
+app.get('/ping', (req, res) => {
+  res.status(200).send('pong')
+});
+
+app.listen(port, '0.0.0.0', () => console.log("Server listen on http://localhost:" + port));