For Tony and Emmy nominee Carrie Coon, set to star in Tracy Letts' Bug on Broadway, nothing says "holiday season" quite like a nerve-shredding descent into paranoia and madness. "I give MTC a lot of credit for making this their Christmas play," she said. In Bug, Coon plays Agnes, a coke-addled divorcée holed up in a seedy motel room on the outskirts of Oklahoma City with Peter (Namir Smallwood), a PTSD-ravaged G…