feat(gossipsub): introduce backpressure

protocols/gossipsub/CHANGELOG.md

@@ -13,6 +13,13 @@
 - Attempt to publish to at least mesh_n peers when flood publish is disabled.
   See [PR 5578](https://github.com/libp2p/rust-libp2p/pull/5578).
 
+- Introduce back pressure and penalize slow peers. Drop stale messages that timeout before being
+  delivered.
+  See [PR 5595](https://github.com/libp2p/rust-libp2p/pull/5595).
+- Change `Behaviour::unsubscribe` and `Behaviour::report_message_validation_result`
+  to `bool` they don't need to be a `Result`.
+  See [PR 5595](https://github.com/libp2p/rust-libp2p/pull/5595).
+
 ## 0.47.0
 
 <!-- Update to libp2p-swarm v0.45.0 -->

protocols/gossipsub/Cargo.toml

@@ -14,13 +14,15 @@ categories = ["network-programming", "asynchronous"]
 wasm-bindgen = ["getrandom/js", "futures-timer/wasm-bindgen"]
 
 [dependencies]
+async-channel = "2.3.1"
 asynchronous-codec = { workspace = true }
 base64 = "0.22.1"
 byteorder = "1.5.0"
 bytes = "1.6"
 either = "1.11"
 fnv = "1.0.7"
 futures = { workspace = true }
+futures-timer = "3.0.2"
 getrandom = "0.2.15"
 hex_fmt = "0.3.0"
 web-time = { workspace = true }
@@ -38,7 +40,6 @@ tracing = { workspace = true }
 
 # Metrics dependencies
 prometheus-client = { workspace = true }
-futures-timer = "3.0.3"
 
 [dev-dependencies]
 hex = "0.4.2"
@@ -48,7 +49,7 @@ libp2p-noise = { workspace = true }
 libp2p-swarm-test = { path = "../../swarm-test" }
 quickcheck = { workspace = true }
 tracing-subscriber = { workspace = true, features = ["env-filter"] }
-tokio = { workspace = true, features = ["rt", "rt-multi-thread", "time"] }
+tokio = { workspace = true, features = ["rt", "rt-multi-thread", "time", "macros"] }
 
 # Passing arguments to the docsrs builder in order to properly document cfg's.
 # More information: https://docs.rs/about/builds#cross-compiling