The world’s biggest hotel company is betting that factory-built guest rooms are a key to juicing revenue — and helping guests get a better night’s sleep.Marriott International Inc. is laying plans for what it says will be the tallest modular hotel in the world, in Manhattan’s NoMad neighborhood. Its 168 guest rooms will be assembled in a factory in Poland, shipped overseas and trucked into New York in the middle of the night, when the city streets can accommodate the oversized loads. The 26-story AC Hotel is expected to rise in 90 days and open next year. Marriott wants the tower to serve as a beacon to developers, lenders and factory owners.