refactor!: port to iroh@0.90 and n0-snafu (#77)

## Description

* Updates to `iroh@main` for 0.90 release
* Replaces thiserror and anyhow with `snafu` and `n0_snafu`
* Makes use of the new `Endpoint::node_addr()` watcher to simplify the address update code

## Breaking Changes

* `net::GossipBuilder::spawn()` is now sync and infallible
* `net::Error` now only has a single variant `ActorDied`, and implements error traits via snafu instead of thiserror

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR. -->

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text), if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

Author: Frando

.github/workflows/ci.yaml

@@ -16,7 +16,7 @@ env:
   RUST_BACKTRACE: 1
   RUSTFLAGS: -Dwarnings
   RUSTDOCFLAGS: -Dwarnings
-  MSRV: "1.81"
+  MSRV: "1.85"
   SCCACHE_CACHE_SIZE: "50G"
   IROH_FORCE_STAGING_RELAYS: "1"