feat(request-response): add modules for json and cbor messages

This patch adds two modules to `libp2p::request_response`:

- `cbor`
- `json`

Both define a `Behaviour` type-alias that comes with a `Codec` implementation which uses the respective `serde` crate to serialize and deserialize the messages.

Fixes #3905.

Pull-Request: #3952.

examples/file-sharing/src/network.rs

@@ -60,7 +60,7 @@ pub(crate) async fn new(
         transport,
         ComposedBehaviour {
             kademlia: Kademlia::new(peer_id, MemoryStore::new(peer_id)),
-            request_response: request_response::Behaviour::new(
+            request_response: request_response::Behaviour::with_codec(
                 FileExchangeCodec(),
                 iter::once((
                     StreamProtocol::new("/file-exchange/1"),