By Go Nakamura and Brad Brooks HOUSTON (Reuters) – Texas officials warned of “disasters within the disaster” of historic cold weather that left millions without heat for a third day on Wednesday, telling residents to prepare for energy to not return until the weekend. Residents in over 100 counties in Texas have been told to boil their drinking water as treatment plants continue to suffer from energy blackouts, officials said. Upward of 12 million people in the state — the country’s second largest with a population of roughly 29 million — have either have no drinking water on tap in their ho…