feat(http/prom): introduce NewRecordStatusCode middleware#4298

cratelyn merged 3 commits intomainlinkerd/linkerd2-proxy:mainfrom

kate/decouple-record-response.pt-1.status-code-middlewarelinkerd/linkerd2-proxy:kate/decouple-record-response.pt-1.status-code-middlewareCopy head branch name to clipboard