feat(http/retry): model PeekTrailersBody<B> with Frame<T>#3559

cratelyn merged 6 commits intomainlinkerd/linkerd2-proxy:mainfrom

kate/http-retry.prepare-peek-trailers-body-for-http-body-1.0linkerd/linkerd2-proxy:kate/http-retry.prepare-peek-trailers-body-for-http-body-1.0Copy head branch name to clipboard