WASHINGTON — The Supreme Court on Thursday unanimously revived whistleblower lawsuits claiming that supermarket and pharmacy chains SuperValu and Safeway overcharged government health-care programs for prescription drugs by hundreds of millions of dollars.The decision gives the whistleblowers another chance to pursue their claims that the companies defrauded the Medicare and Medicaid programs when they reported retail prices for generic prescription drugs, even though they had mainly been sold to customers at deeply …