The list of cities that can count themselves as “springboards to Broadway” is brutally short: Chicago, Boston, maybe Atlanta. And yet, a string of small playhouses in Southern California has somehow become a favorite of the New York crowd over the years, and claimed its place as one of the top regional theaters in America. 40 years after its birth in a hardware store, South Coast Repertory has given birth to “Pulitzer Prize winners like Margaret Edson’s ‘Wit,’ Nilo Cruz’s ‘Anna in the Tropics,’ and [South Coast co-founder Donald] Margulies’s “Dinner With Friends.”