WESTCHESTER COUNTY, N.Y. – Carrie Coon lives right on the edge – of overwhelming sadness, of righteous fury, of whatever emotion bubbles inside the character she is playing, threatening to boil over. In her breakout television role as a woman who loses her family in the apocalyptic drama “The Leftovers,” Coon appears collected while always just an unwanted reminder away from anguished waterworks. In “The Gilded Age,” perceived slights often drive her character, the social-climbing wife of a robber baron, to the brink of indignant tantrums.