LONDON (Reuters) - Stocks rose tentatively on Tuesday as investors picked through the rubble of conflagrations in some of the world’s top economies amid heightened uncertainty over Brexit, a China-U.S. trade war and French protests. FILE PHOTO: Pound Sterling notes and change are seen inside a cash register in a coffee shop in Manchester, Britain, September 21, 2018. REUTERS/Phil Noble/File Photo Contact between China and the United States boosted European stocks and U.