By Luc Cohen and Jonathan Stempel NEW YORK (Reuters) -U.S. prosecutors on Thursday unveiled criminal charges accusing the Russian billionaire Oleg Deripaska of violating sanctions imposed after Russia invaded Ukraine. Deripaska, the 54-year-old founder of aluminum giant Rusal, was among two dozen Russian oligarchs and government officials blacklisted by Washington in 2018 in reaction to Russia’s alleged meddling in the 2016 U.S. election to help Donald Trump become president. The U.S. Department of Justice said Deripaska violated sanctions by using the U.S. financial system to maintain three l…