Running tests with coverage causes CPU to hit 100% after tests finish

* **Version**: v18.14.0
* **Platform**: windows-latest, ubuntu-latest and macos-latest GitHub CI images

When running tests with coverage in CI, after the test run completes successfully, CPU spikes to 100% and the process hangs.

It happened in this build: https://github.com/ipfs/aegir/actions/runs/4225847659/jobs/7338650232 and sometimes happens locally too, though it's a lot more frequent in CI.

This started happening with node 18, it didn't seem to happen with node 16.

The command being run is similar to:

```
c8 --reporter json --report-dir .coverage --temp-directory /tmp/some-random-string --clean mocha test/node.{js,cjs,mjs} test/**/*.spec.{js,cjs,mjs} dist/test/node.{js,cjs,mjs} dist/test/**/*.spec.{js,cjs,mjs} --ui bdd --require source-map-support/register --timeout=60000 --bail
```