feat(quic): promote to stable release

- Cut a stable release of `libp2p-quic`.
- Export `libp2p-quic` as `libp2p::quic`.
- Update examples to use `libp2p-quic` through `libp2p`.

Pull-Request: #4325.

examples/dcutr/src/main.rs

@@ -35,11 +35,10 @@ use libp2p::{
     },
     dcutr,
     dns::DnsConfig,
-    identify, identity, noise, ping, relay,
+    identify, identity, noise, ping, quic, relay,
     swarm::{NetworkBehaviour, SwarmBuilder, SwarmEvent},
     tcp, yamux, PeerId,
 };
-use libp2p_quic as quic;
 use log::info;
 use std::error::Error;
 use std::str::FromStr;