Vera Wang chose warmth over fashion on a chilly New York night. The designer was spotted at Upper East Side restaurant Primola on Saturday in all black — topped off with a black aviator cap with ear flaps. “She sat down with the hat on . . . and it was on when she left,” said a spy who saw Wang with husband Arthur Becker and eight guests. At another table were author/ex-prosecutor Linda Fairstein and Bronx Supreme Court Justice Ann M. Donnelly.