Tests on Windows leaving behind orphaned processes

At the end of the GitHub actions run there are a handful of orphaned processes left when running on Windows, e.g from [this run](https://github.com/eclipse-cdt-cloud/cdt-gdb-adapter/actions/runs/5468269430/jobs/9955669269?pr=276#step:21:1):

```
Cleaning up orphan processes
Terminate orphan process: pid (1176) (gdbserver)
Terminate orphan process: pid (4968) (empty)
```

The tests should be cleaning up better after themselves. I think the ones that are left behind are the tests that are checking error conditions, but it is pretty hard to tell just from the log which they are.

The title says "Windows", but my guess is that on Linux they simply aren't orphaned because when mocha exits it is fully terminating all child processes on Linux and not doing it on Windows. But ideally the test itself should cleanup after itself and not wait until the mocha exits.