Turbopack: keep side-effect-full imports (#76545)
This was already fixed by https://github.com/vercel/next.js/pull/77640 in the meantime
Adds a test for https://github.com/vercel/next.js/issues/76464
```js
// Inside a sideEffect: free module, ...
// ...imports without any bindings are completely dropped, even
// if they reference modules which have `sideEffects: true`
import "./this-module-has-sideEffects";
```
