tools: include exit code in test failures

Include the exit code in test failures. This will give us more
information during the currently-puzzling failures that provide no
information in CI such as:

```
03:10:10 not ok 563 parallel/test-fs-truncate
03:10:10   ---
03:10:10   duration_ms: 1.119
03:10:10   severity: fail
03:10:10   stack: |-
03:10:10   ...
```

PR-URL: https://github.com/nodejs/node/pull/19855


Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Rod Vagg <rod@vagg.org>