WASHINGTON — The Supreme Court opens a new term with Republicans on the cusp of realizing a dream 50 years in the making, a solid conservative majority that might roll back abortion rights, expand gun rights and shrink the power of government.Eight justices are getting back to work Monday at a most unusual, politically fraught moment in American history. They’re still mourning the death of their colleague Justice Ruth Bader Ginsburg, the leader of the court’s liberal wing. They’re working in the …