A proposed $1 billion bailout plan to rescue Nuvance Health, the financially struggling parent company of Danbury and Norwalk hospitals, faced scrutiny during a public hearing in Hartford. Northwell Health, a major New York-based health system, aims to take over Nuvance, which has reported $370 million in losses over the past three years. State regulators grilled Northwell executives about their promise to stabilize finances within five years, as well as their long-term commitment. But Mark Solazzo, Northwell’s chief operating officer, assured officials, saying “We have never closed a hospital, and we don’t intend to.”