feat(perf): implement libp2p perf protocol

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.

protocols/perf/src/lib.rs

@@ -0,0 +1,31 @@
+// Copyright 2023 Protocol Labs.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! Implementation of the [libp2p perf protocol](https://github.com/libp2p/specs/pull/478/).
+//!
+//! Do not use in untrusted environments.
+
+#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
+
+pub mod client;
+mod protocol;
+pub mod server;
+
+pub const PROTOCOL_NAME: &[u8; 11] = b"/perf/1.0.0";