It’s a chicken-and-egg problem: Restaurants are struggling with record-high U.S. egg prices, but their omelets, scrambles and huevos rancheros may be part of the problem. Breakfast is booming at U.S. eateries. First Watch, a restaurant chain that serves breakfast, brunch and lunch, nearly quadrupled its locations over the past decade to 570. Eggs Up Grill has 90 restaurants in nine southern states, up from 26 …