The template for "Most Wanted," which begins a two-week workshop production today at La Jolla Playhouse, is the life of Andrew Cunanan, an alluring, chameleonic party boy from the San Diego gay-bar scene. In 1997, he went on an unexplained, 2 1/2 -month cross-country killing spree, climaxing in his infamy-sealing trophy killing of fashion designer Gianni Versace.