refactor: Use iroh_net::PeerAddr more

[Frando]

Description

Replaces custom types with iroh_net::PeerAddr

Notes & open questions

na

Change checklist

• Self-review.
• Documentation updates if relevant.
• Tests if relevant.

[divagant-martian]

I actually did more or less just this in #1488 based on #1486 with a different take, since I need to serialize the (derp_region, endpoints) by itself (just like gossip does), thus using it there as well.

Can you take a look? I think in principle our object is the same and I would then add the convenience methods you created like with_derp_region to extend the api in the same fashion

[Frando]

Alright, yes this is pretty similar.

We can bikeshed if we want to keep the NodeAddr type to combine the node id and the addr info and use that for connect as in this PR, or change connect to take node id, addr info, and alpn.

So it would be one of these two:

MagicEndpoint::connect(&self, node_id: PublicKey, addr_info: AddrInfo, alpn: &[u8]);
MagicEndpoint::connect(&self, addr: NodeAddr, alpn: &[u8])

I still kinda like the latter, because in most situations you will get the full NodeAddr from somewhere and can just pass it through. But either works fine. What do others think?

But let's maybe get #1488 in first and then I can update this PR afterwards.