Implement libp2p/specs#538

We want a light weight implementation that is just the protocol client and the protocol server. The protocol client will implement /libp2p/autonat/2/dial and the server will handle this.

The logic of address management: which addresses to verify and when will live inside Address Pipeline Service(provisional name) as described here. This Address Pipeline will have to implement a user of this AutoNATv2 client with logic similar to one described here

One important benefit of merging just the protocol client and the server into master first is, this protocol will be unusable till some threshold percentage(maybe 10?) of nodes upgrade and start supporting this because before reaching this threshold, AutoNATv2 nodes will not be able to find any AutoNATv2 peers.