orchestrator: drop created k8s service

[uce]

We create a Kubernetes service and stateful set, but never delete the service on drop. I added the service delete call to the orchestrator and updated the existing smoketests to verify that services are cleaned up.

Fixes #14188.

Motivation

• This PR fixes a recognized bug.

  #14188

Tips for reviewer

@benesch Please feel free to close this PR directly and rewrite. I was only curious to use cloudtest and check the local testing setup. Take this PR mainly as a confirmation of the reported issue.

I haven't written Rust or Python in a while. I added exists.py and followed the lead from wait.py, but it doesn't feel terribly idiomatic to me.

Checklist

• [x] This PR has adequate test coverage / QA involvement has been duly considered.
• [X] This PR includes the following user-facing behavior changes:

[uce]

Thanks for reviews! I'll merge once CI passes.

@pH14 I created https://github.com/MaterializeInc/materialize/issues/14918 to track your suggested refactoring.