Adam B. Vary Senior Entertainment WriterWhile “The Flash” is already set to speed back to the CW for its eighth season, two of its original stars are staying behind: Carlos Valdes and Tom Cavanagh are both officially leaving the show after Season 7.Cavanagh — who played several alternate versions of the brilliant and prickly scientist Harrison Wells (as well as Flash nemesis Eobard Thawne) — was technically set to end his tenure as a series regular with Season 6.