How to turn the bloody truths of the Iraq war into mass entertainment is a problem that has repeatedly bedeviled Hollywood executives. Even “The Hurt Locker,” which won the Academy Award for best picture last year, earned only $17 million domestically. Now Broadway, where the price of a ticket can be 10 times as much as at the multiplex, is taking its first major look at Iraq eight years after the invasion, with a play that starts with a behanding, descends into brutality and murder, and features no less than Uday Hussein clutching the severed head of his brother, Qusay.