Allows folks like @bajtos to use the crate, see https://github.com/filecoin-station/zinnia/pull/85.
I opted for not exposing the crate through the `libp2p` meta crate as it is a testing tool only. @thomas
let me know if you prefer me to do so.
Pull-Request: #3629.
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.