A grandson and nephew of Chicago’s two longest-serving mayors was convicted Monday of tax crimes and making false statements.Patrick Daley Thompson, the 11th Ward alderman, must immediately resign under state law.Thompson was accused of falsely claiming mortgage interest deductions and lying about lines of credit from Washington Federal Bank for Savings.The jury’s deliberations and verdict followed about three hours of closing arguments.Thompson’s grandfather was Richard J. Daley and his uncle is Richard …