By Herbert Lash and Marc Jones NEW YORK/LONDON (Reuters) – World shares slid on Monday while oil prices jumped to seven-year highs on U.S. warnings that Russia could soon invade Ukraine, and investors scurried to buy safe-haven government bonds they mostly shunned so far this year. Europe’s STOXX 600 share index tumbled as much as 3.0% and spot gold headed toward its biggest single-day gain in four months even as Russia suggested it was ready to keep talking to the West to defuse the crisis. The United States is relocating its embassy operations in Ukraine from the capital Kyiv to the western …