By Eric Onstad LONDON (Reuters) – EU policymakers have launched a drive to restart domestic output of magnesium, used in aluminium and steel products, with at least three firms working on projects, according to documents and officials. A European Commission staff working document made available to Reuters places a new emphasis on magnesium and a target of cutting dependence on major producer China, saying investment of up to 2 billion euros ($2.12 billion) will be needed to restart smelting activity in Europe by 2025. The issue has gained importance for Europe, which consumes a fifth of the gl…