Show HTTP response code for Kubernetes errors

What does this MR do?

Show HTTP response code when Kubernetes errors (but not anything else)

Also a Tidy up: Instead of raising Kubeclient::HttpError then check-for-404, use Kubeclient::ResourceNotFoundError

What are the relevant issue numbers?

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/53628

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• [-] Conforms to the style guides
• [-] Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.