BY GINA LEE RONHOVDE “Must Be Thick-Skinned.” There is a common job description in Hollywood want ads that say, “Must Be Thick-Skinned.” What does that mean, exactly? Well, first of all, Hollywood can be simultaneously wonderful and beyond horrifying. When it comes to show business, everything depends on whom you know, what you can offer, and how you play the game. It’s no secret that Tinseltown is a challenge all in its own. But what you may not realize is the unofficial “In