request timeout when receiving NOT_LEADER error the first time

Request timeout when receiving NOT_LEADER error the first time.

The reason is that [error.toString](https://github.com/tikv/client-java/blob/v3.1.9/src/main/java/org/tikv/common/operation/RegionErrorHandler.java#L95) will trigger JVM ClassLoadr load grpc error related classes, which costs more than 100ms.