STOCKTON — The tidy sum of $1.8 billion sounds like a lot of money, but billions don’t go nearly as far as they once did.Just ask San Joaquin County officials, who will bring the proposed 2019-20 fiscal-year budget of just more than $1.8 billion before the Board of Supervisors on Tuesday.The proposed budget is more than $40.8 million larger than the 2018-19 fiscal-year budget, which expires June 30.