The world’s biggest energy companies have a tough decision to make amid languishing oil prices: Do they keep their coveted investment-grade credit ratings or maintain century-old practices of paying shareholders annual dividends worth billions in cash? Exxon Mobil Corp. and its peers are grappling with the collision course between the two, which appears unavoidable as crude continues to hover around $30 a barrel. Even with announced spending cuts that exceed $92 billion, producers are losing money on almost every barrel…