Parallel PolicyServer controller test execution and clean-up

[fabriziosestito]

Is your feature request related to a problem?

At the moment we run the policy controllers test in parallel (on a real cluster) However, running the envtest integration tests of the PolicyServer results in failures. We would like to run these tests in parallel, refactoring what is needed to comply with idiomatic ginkgo.

Also, it would be nice to:

• [ ] check if this helper: https://github.com/kubewarden/kubewarden-controller/blob/235d006250ac38f57e6f5e6630aabbca7e58ace7/internal/controller/utils_test.go#L331 is needed everywhere

• [ ] By switching to a client created in the test suite and by not using the manager client (which is wrong, since this client is using the cache now) we are getting empty GroupVersionKind when fetching PolicyServer resources. This causes certain assertions to fail. The assertions are marked by a FIXME comment