feat(iroh-net): persist known peer info (#1488)

## Description

Rough list of changes
- add an option to the `MagicEndpointBuilder` to set the path in which
peers are saved. This is used to read peers on start up and store them
on an interval and on shutdown.
- add `KnownPeers` to ease serializing and deserializing peer info
- move the logic of `add_known_addr` to the `PeerMap` to facilitate
instantiating from a known peer list
- Add an `IrohPath` for the peers.
- Add an option to the `Node`s builder to set the path, passed down to
the endpoint.
- For serialization it makes sense to have an object modelling the peer
addressing info. This is the `AddrInfo`, which now replaces the custom
`IrohInfo`

## Notes & open questions

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## Change checklist

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