California is poised for a swift transformation of its electricity landscape — and that could bring tumult if preparations aren’t made soon to maintain quality and avoid reliability problems like rolling blackouts, the state’s leading energy regulator is warning. After decades of dominance by investor-owned utilities, electricity markets in the state are becoming more competitive. Ratepayers today have a growing number of choices for powering their lights, laptops and electric cars — from installing rooftop solar panels and consumer-scale batteries to joining increasingly popular government-run electricity programs known as community choice aggregation, or CCA.