WASHINGTON — The Supreme Court on Thursday rejected a nationwide settlement with OxyContin maker Purdue Pharma that would have shielded members of the Sackler family who own the company from civil lawsuits over the toll of opioids but also would have provided billions of dollars to combat the opioid epidemic. After deliberating more than six months, the justices in a 5-4 vote blocked an agreement hammered out with state and local governments and victims.