Add new key io-thread in client info

Redis 8.0 introduces new key `io-thread` in the response
for client info. The key needs to be parsed. If an unknown key
is observed, the client will return an error.

command.go

@@ -5114,6 +5114,7 @@ type ClientInfo struct {
 	OutputListLength   int           // oll, output list length (replies are queued in this list when the buffer is full)
 	OutputMemory       int           // omem, output buffer memory usage
 	TotalMemory        int           // tot-mem, total memory consumed by this client in its various buffers
+	IoThread           int           // io-thread id
 	Events             string        // file descriptor events (see below)
 	LastCmd            string        // cmd, last command played
 	User               string        // the authenticated username of the client
@@ -5292,6 +5293,8 @@ func parseClientInfo(txt string) (info *ClientInfo, err error) {
 			info.LibName = val
 		case "lib-ver":
 			info.LibVer = val
+		case "io-thread":
+			info.IoThread, err = strconv.Atoi(val)
 		default:
 			return nil, fmt.Errorf("redis: unexpected client info key(%s)", key)
 		}