feat: introduce the dual WAN/LAN DHT

[Stebalien]

And only join the WAN DHT if we're publicly reachable.

TODO:

• Enable AutoNATService by default on all DHT nodes?
• Add more tests.

[Stebalien]

Testing Plan:

1. Make a network of 50 nodes with loopback addresses, and a network of 50 nodes with WAN addresses.
2. Add one node to both network.
3. Verify that the node on both networks can find a peer they're not already connected two on both networks.

The test should use the "mock" network and should live in the "integration" test folder. We can model it after https://github.com/ipfs/go-ipfs/blob/5ecf44a88217f46472aa535a54153edc2e2bede6/test/integration/three_legged_cat_test.go#L67-L150.

Gotchas:

• The mocknet doesn't make any effort to pick the right source/target IP when creating a fake connection. That should be fine in this case as long as only the test node lives on both networks. All other nodes only live on one or the other.

@willscott think you could pick this up?

[willscott]

integration test to merge into this branch in #7151

[Stebalien]

I'm going to merge this for now given that we now have a test PR and we're not going to ship a release without this.