Fix config import on Windows and disable test in failing envs (#29971)
Follow-up to https://github.com/vercel/next.js/pull/29935 this fixes the failing tests on Azure as it seems the `import()` needs to be prefixed with `file://` on Windows or an error is thrown. It also disables the config unit tests since a dynamic import inside of `jest` on either an m1 on macOS or Windows using node 14 causes a segfault from being used inside of `vm`.
<details>
<summary>segfault error in jest</summary>
<img width="962" alt="Screen Shot 2021-10-15 at 16 45 04" src="https://user-images.githubusercontent.com/22380829/137596819-072233e3-1a45-445f-a3dd-c03ec62fb4ce.png">
</details>
<details>
<summary>Windows absolute import error</summary>
<img width="1114" alt="Screen Shot 2021-10-16 at 12 45 59" src="https://user-images.githubusercontent.com/22380829/137597185-200f3164-7f79-488f-acc9-6c812ce5bc4a.png">
</details>