Replace anyhow in public API

[joshka]

Hiya,
I'm watching the p2p chat vid (https://www.youtube.com/watch?v=ogN_mBkWu7o) and noticed that the errors are exposed as anyhow::Result. Ideally this should be custom errors instead.

[joshka]

Closing as I just saw n0-computer/iroh#2741 linked from the roadmap (and wasn't aware that this repo was recently split from the main repo).