By Liz Hampton HOUSTON (Reuters) -Executives at a U.S. energy conference are set to turn their focus on Tuesday to renewables and the long-term shift away from fossil fuels, even as the West seeks immediate replacements for Russian oil and gas supplies after Moscow’s invasion of Ukraine. The CERAWeek energy conference on Houston opened on Monday with crude prices at levels not seen since 2008, putting the focus on how to reduce reliance on Russia, a top global exporter of oil and gas which now faces ever tighter Western sanctions. The United States, which has held talks with allies on banning …