NEW YORK — An accused Brooklyn pimp charged with chopping up one of his sex trafficking victims after he schemed to take out life insurance policies under her name is set to face trial in a federal courtroom. The case against Cory Martin started with a gruesome mystery — the discovery in April 2018 of a young woman’s head and limbless torso in Canarsie Park, facedown and covered with leaves. A day later, police found garbage bags with her limbs inside. Investigators determined the woman was 26-year-old Brandy Odom, after her sister recognized her distinctive tattoo of the word “Chocolate” on h…