`common_verification` v0.2.0 has been released more than a year ago (but
is still the latest version), so it's about time to update.  This also
entails the following changes:

- Instances of modules from `common_verification` in our testbenches are
  updated.
- `common_cells` is updated to v1.21.0 to align on the same version of
  `common_verification`.