Document "Advertise security protocol in multiaddr"

[p-shahi]

A proposal to include the security protocol (TLS or Noise) in the multiaddr is being proposed. This is a performance optimization to reduce time spent in protocol negotiation. go-libp2p is planning to implement this in Q1 2023 and rust-libp2p in Q2 2023.

• The spec draft for this change is here: https://github.com/libp2p/specs/pull/353

Done Criteria

• [x] Updates that describe the change to multiaddr format
• [x] Describes how the security protocol to be used is determined by multiaddr
• [x] Describe the optimization (how 1 RTT is saved)
• [x] Decide where to add this section: under a new Advanced Concepts section, under general connection establishment section? how to reference in docs for secure channels (TLS and Noise). Relates to https://github.com/libp2p/docs/pull/202 and https://github.com/libp2p/docs/issues/19

Why Important

We need to document and highlight the performance optimizations libp2p has specified and implemented.