Finish cleaning up module test_role_v2

Some tests in module `test_role_v2` are focused on filters, not roles. Create a
new module, `test_filter_v2`, and move those tests into the new module.
Significantly clean up the moved tests.
Well, I'm doing a little more than just getting and ID. That can be done with just this code:

```python
filter_id = entities.Filter(
    permission=[permission['id'] for permission in ct_perms],
    role=role_id,
).create()['id']
```

You can then instantiate a `Filter` with that ID:

```python
filter_ = entities.Filter(id=filter_id)
```

I'm just doing those two steps in one go.