PROVIDENCE — Putting a close to an ugly decades-long legal dispute, the state Supreme Court affirmed a ruling throwing out defamation and a host of other claims against disgraced former Central Falls Mayor Charles D. Moreau.The high court on Monday concluded that Superior Court Judge Sarah Taft-Carter was right in rejecting allegations brought against Moreau by former city employees, librarian Thomas Shannahan and Police Chief Thomas Wilson, and two other library staff members.