Cook County Board President Toni Preckwinkle speaks at a news conference last week.Jim Vondruska/Sun-Times As she easily breezed to another two-year term as the head of the Cook County Democratic Party, Toni Preckwinkle touted the dominance the party has held in local elections, but also foreshadowed the work to be done to unify the party behind Democratic President Joe Biden ahead of the national convention in Chicago.Preckwinkle on Monday was…