Unified libp2p graphics and diagrams

As the libp2p documentation gets updated, we also need to update graphics and diagrams. These consist of (but are not limited to)

• High-level descriptions of various protocols
• Abstract networking diagrams
• A mix of "product and process" visuals

and would follow a standard theme.

For upcoming docs on new libp2p optimizations and newly supported protocols, we need a way to display a high level visualization of how the protocols work.
We currently use UML diagrams but they are too low-level (usually better suited for technical specifications and design documents.)

Inspiration can be found here and here.

• Add protocol diagram for DCUtR
• Add protocol diagrams for AutoNAT
• Update Circuit Relay sequence diagram to simple protocol diagrams
• Add protocol/process diagram for multistream
• Add protocol diagram for ping
• Add protocol diagram for identify and identify/push
• Add protocol diagram for WebTransport
• Add protocol diagram for QUIC
• Update the sequence diagrams on the hole punching: https://docs.libp2p.io/concepts/nat/hole-punching/
• Update the OSI diagram in the transports page: https://docs.libp2p.io/concepts/transport/
• Update all diagrams in pubsub page: https://docs.libp2p.io/concepts/publish-subscribe/

Going forward, we will follow the libp2p blog post approach and include new diagrams and graphics as part of the change request. However, given that the open PRs (many documenting protocols and process) have been hanging for some time, we aim to get those merged and add the diagrams shortly after to limit the friction.

In the near term where there is little to no "doc debt", it will be part of the process to request diagrams as documents are created and ship them together.