Port Arti to WASM

This will be a doable but nontrivial undertaking. To achieve it, we'll need to replace everything that uses the filesytsem (state storage, directory cache) to use the appropriate web APIs. We'll also need to write a new tor-rtcompat backend for the wasm use-case. Likely there will be more work as well.

Added tickets:

• #339 — StateMgr implementation
• #340 — Storage implementation for tor-dirmgr
• #341 — Compression libraries, look for pure-Rust implementations
• #342 — Define a wasm/wasi Runtime.
• #343 — Work without TCP sockets.