Rewrite `libp2p-perf` protocol using `libp2p-request-response`. Additionally adjust to latest conventions, e.g. the final JSON output.
Pull-Request: #3646.
Implementation of the libp2p perf protocol according to https://github.com/libp2p/specs/pull/478/.
//CC @MarcoPolo as the author of the specification.
**Don't (yet) expect this to produce reliable performance metrics.**
Pull-Request: #3508.