Replace usage of KubernetesServerTestResource with WithKubernetesTestServer annotation

[shawkins]

WithKubernetesTestServer is a higher level annotation for using the server test resource that also controls the scoping to be per test class, rather than the default of per module (which caused us issues in the past).

[shawkins]

We should be able to do this after fabric8 6.5, which will move us off of okhttp - there's a classloading memory leak with okhttp that is preventing this now.