docs: add initial architecture diagrams for js-libp2p

[maschad]

Title

docs: add initial architecture diagrams for js-libp2p

Description

These diagrams in mermaid are a result of the hard work from @achingbrain @SgtPooki @whizzzkid @wemeetagain and @polus-arcticus at the js-libp2p colo to try give consumers an understanding of our architecture.

This also removes some outdated docs.

Closes #2083

Notes & open questions

This may be a temporarily place to store the docs until #2117 is completed. This list is by no means exhaustive and more scenarios are welcome.

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works