Use `KubernetesClient` to query K8s info.

[xiaomi7732]

I am halfway through this work item. While this will simplify our code eventually, it will be a relative large change for code reviewing, including unit test changes.

To reduce the stress on code reviewers, here are some manual tests that I will finish before submitting a PR:

• [x] Run in K8s Cluster without RBAC
• [x] Run in K8s Cluster with RBAC on
  • [x] With proper RBAC permission for the service account - verify k8s properties are fetch properly.
  • [x] With insufficient permission - verify error messages are output correctly for troubleshooting scenario.
• [x] Hosting startup

To make the test efficient, I'll mix these 2 typical project types into the tests above:

• [x] WebAPI
• [x] Worker For example, I might run WebAPI in K8s Cluster without RBAC, and worker in cluster with RBAC...