Consider advertising all interface addresses and not just the primary interface addrs

[sukunrt]

When a host is listening on 0.0.0.0 we only advertise the primary interface address of the node. The primary interface is selected by querying the routing table for the default route. But if the node is listening on 0.0.0.0, we should advertise all the interface addresses.

Specifically, I want the nodes to advertise the tailscale interface addrs so I can connect to nodes running over my different devices.

The obvious downside here is that we'll start advertising a lot more addresses to the network.