SPRINGFIELD — With a new spring legislative session beginning this week, one lawyer-lawmaker is switching sides at the Capitol.Elgie R. Sims Jr., a Chicago Democrat who has served in the House since 2012, is moving from the House chamber to the Senate. He is replacing longtime Democratic leader Donne E. Trotter, who retired earlier this month.Sims has long been considered Trotter’s protege.Sims, who is of counsel at Foley & Lardner LLP and earned his law degree from Loyola University Chicago School of Law …