Draft: Unreliable+unordered WebRTC data channel transport for Snowflake

This merge request adds a non-production-ready version of snowflake that use udp like transport mode to reduce abstraction cost. Rewritten based on a less graceful version.

There are some script ready for testing: https://gist.github.com/xiaokangwang/3dc8f703879cbd3764f8ed6dfa2da047

To build the code, run build.sh with Dockerfile in the same directory. To start the network, run start_network.sh. See run a client for example for how to get a client working.

Addresses #40352.