By David French (Reuters) – Wall Street’s main indexes ended a seesaw session higher on Monday, as investors turned their attention to this week’s policy meeting at the Federal Reserve and how aggressively it will hike interest rates. Even more so than the Ukraine war or corporate earnings, the actions of the U.S. central bank are driving market sentiment as traders try to position themselves for a rising interest rate environment. The S&P 500 and the Nasdaq rebounded from logging their worst weekly percentage drop since June on Friday, as markets fully priced in at least a 75 basis point rise…