A report by the House Ethics Committee accused former Representative Matt Gaetz, Republican of Florida, of regularly paying for sex and using illegal drugs, and of having sexual relations with a 17-year-old girl in 2017. The report concluded that the actions by Mr. Gaetz — President-elect Donald J. Trump’s former pick for attorney general — violated state sexual misconduct laws, including Florida’s statutory rape law, and violated House rules. But the committee said it did not find conclusive evidence that he violated federal sex trafficking laws.