🐛 Bug Report — Runtime APIs: `require()` of Node built-in module in `nodeJsCompatModule` outside virtual root throws

Hey! 👋 With the following `workerd` configuration:

```capnp
using Workerd = import "/workerd/workerd.capnp";

const config :Workerd.Config = (
services = [
( name = "main", worker = .worker ),
],
sockets = [
( name = "http", address = "*:8080", http = (), service = "main" ),
]
);

const worker :Workerd.Worker = (
compatibilityDate = "2023-08-01",
compatibilityFlags = ["nodejs_compat"],
modules = [
( name = "index.mjs",
esModule = "export { default } from \"./dir/index.cjs\"",
),
( name = "dir/index.cjs",
nodeJsCompatModule =
`const { Buffer } = require("buffer");
`module.exports = {
` async fetch(request, env, ctx) {
` return new Response(Buffer.from("test").toString());
` }
`}
),
],
);
```

...`require("buffer")` throws with `Error: No such module "dir/node:buffer".`. Replacing it with `require("node:buffer")` also exhibits the same error. Replacing `dir/index.cjs` with `index.cjs` fixes the issue.

Start by running the supplied workerd configuration and reproducing the failure from the nested nodeJsCompatModule. Trace how require("buffer") and require("node:buffer") are resolved relative to dir/index.cjs; done means both built-in imports resolve there as they do when the module is at the virtual root.

Written by the indexing model from the issue text.