refactor(iroh-net)!: Rename Endpoint::my_addr to Endpoint::node_addr

[flub]

Description

This is in line with e.g. Endpoint::node_id.

Breaking Changes

• Endpoint::my_addr -> Endpoint::node_addr

Notes & open questions

Other networking APIs tend to have something like "local_addr",
e.g. UdpSocket::local_addr in the standard library or
Endpoint::local_addr in Quinn. Sometimes this is because they also
have a "peer_addr" version, e.g. UdpSocket::peer_addr.

In this light perhaps some of our APIs might benefit from using this
for consistency with other API conventions. In this case this would
become Endpoint::local_node_addr.

We already have Endpoint::local_addr which returns the socket
addresses we are bound to. Other candidates would be:

• Endpoint::home_relay -> Endpoint::local_home_relay
• Endpoint::node_id -> Endpoint::local_node_id
• Endpoint::secret_key -> Endpoint::local_secret_key

But, you can already see this fall apart. Because our endpoint is not
the thing that is connected to a peer (that is the Connection) I don't
think it makes sense to use the term "local" in the APIs.

And perhaps Endpoint::local_addr should be changed anyway, while it is
compatible with other usages it is rather out of tone for us because
we have too many kind of addresses (socket address, node address,
direct address, ...?). So perhaps that one is better off as
Endpoint::bound_sockets or so.

Change checklist

• Self-review.
• Documentation updates if relevant.
• [ ] Tests if relevant.
• All breaking changes documented.