deps(iroh-next): move from igd to igd-next (#2134)

## Description

[`igd`](https://github.com/sbstp/rust-igd) has been archived,
[`igd-next`](https://docs.rs/igd-next) it's a replacement. This still
does not use hyper 1 but will (hopefully) be
[upgraded](dariusc93/rust-igd#4) soon™️

## Notes & open questions

n/a 

## Change checklist

- [x] Self-review.
- [x] Documentation updates if relevant.
- [ ] Tests if relevant.

Author: divagant-martian