Refactor policy tests

[viccuad]

After the work on PolicyGroups, there's quite the repetition on policy tests.

Acceptance criteria

Refactor all the *policy tests to a single test using ginkgo's Table Specs, meanwhile differentiating cluster and namespace-scoped policies. However, we should be careful refactoring this as it could introduce readability issues in the integration tests.

Originally posted by @fabriziosestito in #837 (comment).