NEW YORK — Eighteen former NBA players were charged Thursday with pocketing about $2.5 million illegally by defrauding the league’s health and welfare benefit plan in a scam that authorities said involved claiming fictitious medical and dental expenses.“The defendants’ playbook involved fraud and deception,” U.S. Attorney Audrey Strauss said at a news conference after FBI agents across the country arrested 15 ex-players and one of their wives in a three-year conspiracy that authorities say …