refactor(s2n-quic-dc): use map getter method to replace AsRef for Handshake trait

[boquan-fang]

Release Summary:

Resolved issues:

related to #2741, and #2744.

Description of changes:

After some review, I decided to not use a AsRef trait to retrieve the secret::Map that's associated with the client and server tokio builders:

s2n-quic/dc/s2n-quic-dc/src/stream/server/tokio.rs

Lines 29 to 31 in b1245b8

	pub trait Handshake: AsRef<secret::Map> + Clone {
	fn local_addr(&self) -> SocketAddr;
	}

s2n-quic/dc/s2n-quic-dc/src/stream/client/tokio.rs

Lines 31 to 39 in b1245b8

	pub trait Handshake: AsRef<secret::Map> + Clone {
	/// Handshake with the remote peer
	async fn handshake_with_entry(
	&self,
	remote_handshake_addr: SocketAddr,
	) -> std::io::Result<(secret::map::Peer, secret::HandshakeKind)>;
	fn local_addr(&self) -> std::io::Result<SocketAddr>;
	}

Instead, we can just add a map method to extract the secrete::Map. Using the AsRef trait is hard to remove in the future and this Handshake trait is just a temporary solution to the fact that some methods hasn't been implemented.

Call-outs:

Testing:

I did internal integration test for this.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.