Handle in test that a `OutboundProbeEvent::Response` can be reported
before the associated inbound connection event.
In rare cases (that only really happen in a test setup where both peers
run on the same device) the server may observe a connection and report
the response back to the client, before the connection event was
reported at the client.
This commit adds a behaviour protocol that implements the AutoNAT specification.
It enables users to detect whether they are behind a NAT. The Autonat Protocol
implements a Codec for the Request-Response protocol, and wraps it in a new
Network Behaviour with some additional functionality.
Co-authored-by: David Craven <david@craven.ch>
Co-authored-by: Max Inden <mail@max-inden.de>