Reuse the swh.core.db.pytest_plugin factory
```
|---------+--------------+-------------+----------------|
| machine | before (min) | after (min) | note |
|---------+--------------+-------------+----------------|
| laptop | 1:22.73 | 0:45.525 | `time tox` |
| jenkins | 1:23 | 1:00 | jenkins report |
|---------+--------------+-------------+----------------|
```