This week’s new entertainment releases includes a new album from pop heartthrob Shawn Mendes and separate Christmas TV specials from Carrie Underwood and Mariah Carey. The 11th and final season of the Showtime dramady “Shameless” debuts Sunday, tackling the pandemic, urban gentrification and personal pressures. Netflix has a new two-part series about the life of Selena Quintanilla, the breakthrough star in male-dominated Tejano music, played by Christian Serratos. And the live-action “Mulan” will finally be free for Disney+ subscribers on Friday. The animated 1998 version is also available on that service for comparison sake.