feat: migrate to quick-protobuf

Instead of relying on `protoc` and buildscripts, we generate the bindings using `pb-rs` and version them within our codebase. This makes for a better IDE integration, a faster build and an easier use of `rust-libp2p` because we don't force the `protoc` dependency onto them.

Resolves #3024.

Pull-Request: #3312.

protocols/identify/src/mod.rs

@@ -0,0 +1,2 @@
+// Automatically generated mod.rs
+pub mod structs;