SHUFFLING THE DECK: High school play starts Sept. 10, and league realignment has created interesting situations. Two firsts: The three Irvine schools--Irvine, University and Woodbridge--are in the same league, the expanded Sea View. And three Catholic schools found homes in county public leagues--Mater Dei (South Coast), Servite (Sunset) and Santa Margarita (Sea View). . . . Mater Dei's entrance into the always powerful South Coast is expected to have the biggest impact.