basichost: use autonatv2 to verify reachability

fix slice ownership

Author: sukunrt

core/event/reachability.go

@@ -2,6 +2,7 @@ package event
 
 import (
 	"github.com/libp2p/go-libp2p/core/network"
+	ma "github.com/multiformats/go-multiaddr"
 )
 
 // EvtLocalReachabilityChanged is an event struct to be emitted when the local's
@@ -11,3 +12,12 @@ import (
 type EvtLocalReachabilityChanged struct {
 	Reachability network.Reachability
 }
+
+// EvtHostReachableAddrsChanged is sent when host's reachable or unreachable addresses change
+// Reachable and Unreachable both contain only Public IP or DNS addresses
+//
+// Experimental: This API is unstable. Any changes to this event will be done without a deprecation notice.
+type EvtHostReachableAddrsChanged struct {
+	Reachable   []ma.Multiaddr
+	Unreachable []ma.Multiaddr
+}