[DPL-2013] Logging improvements

[alyssaruth]

I've been looking at a flavour of flakiness that involves some kind of slow call to test control, this PR is making various logging improvements that would've made this easier:

• Add a UUID to request/response logs so they can be correlated
• Add request duration for successful calls
• Tweak the logic so 4xx / 5xx responses are logged as errors, instead of lines like this which are annoying to try and hunt for:

{"message":"2025-08-04T21:08:39.350414645Z stderr F 2025/08/04 21:08:39 Success forwarding request /io-pkb-testcontrol-clearInternalState to upstream phr-webapp at http://phr-webapp-k8s113-ms1.pkb.svc.cluster.local/.:9876: 500"}