COLOGNE, Germany — Germany’s KNDS this week unveiled the Leopard 2A8, the latest version of the venerable main battle tank that has become a staple of armored formations for more than a dozen countries in Europe and beyond. The tank will be a new build, the first for the Leopard series since 1992, according to German defense officials, after several previous versions that were modernizations of existing tanks. The German army is slated to get 123 of the behemoths weighing nearly 70 metrics ton,