By Tom Sims, Alexander Hübner and Jonathan Stempel NEW YORK/MUNICH (Reuters) -Germany’s Allianz SE agreed to pay more than $6 billion and its U.S. asset management unit pleaded guilty to criminal securities fraud over the collapse of a group of investment funds early in the COVID-19 pandemic. Allianz’s settlements with the U.S. Department of Justice and U.S. Securities and Exchange Commission are among the largest in corporate history, and dwarf earlier settlements obtained under President Joe Biden’s administration. Gregoire Tournant, the former chief investment officer who created and oversa…