Barbecue sides like Sichuan collards and cardamom cornbread are shaking up the traditional format — and diners can't get enough.Credit: Photo by Jessica Attie / LeRoy & LewisOn most barbecue menus across the United States, traditional sides like slaw, beans, and potato salad are common. But a growing number of pitmasters and chefs are expanding how the category is defined. Sides have become a place where chefs can express their regional identity…