multi: Added Tor support

This commit adds Tor support. Users can set the --TorSocks flag
to specify which port Tor's SOCKS5 proxy is listening on so that
lnd can connect to it. When this flag is set, ALL traffic gets
routed over Tor including DNS traffic. Special functions for
DNS lookups were added, and since Tor doesn't natively support
SRV requests, the proxySRV function routes connects us to
a DNS server via Tor and SRV requests can be issued directly
to the DNS server.

Co-authored-by: MeshCollider <dobsonsa68@gmail.com>

channeldb/nodes.go

@@ -275,7 +275,10 @@ func deserializeLinkNode(r io.Reader) (*LinkNode, error) {
 			return nil, err
 		}
 
-		addr, err := net.ResolveTCPAddr("tcp", addrString)
+		// We use the general resolveTCP function in case a separate
+		// resolver was specified in the SetResolver function. By
+		// default resolveTCP = net.ResolveTCPAddr.
+		addr, err := resolveTCP("tcp", addrString)
 		if err != nil {
 			return nil, err
 		}