By Nate Raymond (Reuters) – Consulting firm McKinsey & Co has agreed to pay $78 million to resolve claims by U.S. health insurers and benefit plans that it fueled an epidemic of opioid addiction through its work for drug companies including OxyContin maker Purdue Pharma. The settlement was disclosed in papers filed on Friday in federal court in San Francisco. It marked the last in a series of settlements McKinsey has reached resolving lawsuits over the U.S. opioid epidemic. Plaintiffs accused McKinsey, one of the leading global consulting firms, of contributing to the deadly drug crisis by hel…