basic_host: close swarm on Close (#2916)

Using the `BasicHost` constructor transfers the ownership of the swarm.
This is similar to how using `libp2p.New` transfers the ownership of
user provided config options like `ResourceManager`, all of which are
closed on `host.Close`

p2p/host/basic/basic_host.go

@@ -1080,6 +1080,10 @@ func (h *BasicHost) Close() error {
 		_ = h.emitters.evtLocalProtocolsUpdated.Close()
 		_ = h.emitters.evtLocalAddrsUpdated.Close()
 
+		if err := h.network.Close(); err != nil {
+			log.Errorf("swarm close failed: %v", err)
+		}
+
 		h.psManager.Close()
 		if h.Peerstore() != nil {
 			h.Peerstore().Close()