Metrics are timed separately for each retry

The Metrics RFC (https://docs.google.com/document/d/1BAPS8bPMv8-4FPIdysgpxEsKrUgd595EAGOU-_nXHRY/edit?pli=1#heading=h.68c8u56woaes) states that operation duration metrics should be measured surrounding the entire operation attempt, including retries.

Response Latency in microseconds  which covers the complete request / response cycle (think: “outer request span latency”, covering encode, dispatch, retries etc). Note: for bulk operations, each individual request counts individually.

Instrumented at: when the response has been decoded, before it is marked as completed towards the user

Currently, the .NET SDK is measuring and reporting metrics for each attempt when there are retries. There appears to be some logic that is "summing" the attempts, I'm not sure precisely what that is doing, but is definitely outputting a value for each attempt regardless.