By Caroline Valetkevitch NEW YORK (Reuters) – Stocks on global indexes mostly edged higher in volatile trading on Monday, extending last week’s sharp gains, while oil prices and Treasury yields rose. Oil was up following last week’s rout, with investors still weighing worries over an economic slowdown against concern over lost Russian supply amid sanctions related to the conflict in Ukraine. Investors have been hoping oil’s slide from three-month peaks hit earlier in June could ease overall inflation concerns and allow the U.S. Federal Reserve to tighten policy less aggressively than initially…