Set up test harness or unit test framework to exercise Kubernetes integrations

This is difficult to add an automated test for at this point because the "new" (since 3.0) test framework doesn't really have any traditional unit tests. Even the unit tests actually build and run the whole process and hit some actual testcontainers dependency services. In order to add a test for this bug we would need a much more robust discovery test harness that can exercise Kubernetes discovery (or any other discovery that allows for multilevel trees where these node collisions can appear). Or else we would need to set up a traditional unit test that exercises only the DiscoveryNode class, or Kubernetes API discovery class, and uses simple mocks for things like the k8s API client - but then this entails setting up a lot of other mock dependencies like a database, so it becomes quite complicated.

_Originally posted by @andrewazores in https://github.com/cryostatio/cryostat/issues/901#issuecomment-2863530823_