Alabama lawmakers overwhelmingly advanced legislation on Thursday that would shield doctors, clinics and hospitals offering in vitro fertilization treatment, clearing a major hurdle in their race to enshrine protections for reproductive medicine into law.The scramble comes after a State Supreme Court ruling this month found that, under Alabama law, frozen embryos should be considered children, upending I.V.F. treatment across the state and leading multiple clinics to stop offering the treatments to avoid possible liability.The Senate unanimously passed its version of the measure, while the…