SPRINGFIELD — For years, the first step for lawmakers in the budget-making process was to adopt a state revenue estimate.The House and Senate would agree on an amount to spend for the upcoming fiscal year and then build a plan around that figure.It hasn’t happened during the 2-year-old budget impasse between Republican Gov. Bruce Rauner and legislative Democrats.But now House Republicans have asked the state’s top lawyer to force the issue, sending her a letter this week that cites the state constitution, …