Emails from Hillary Clinton’s private server were found after the F.B.I. seized electronic devices once shared by Anthony D. Weiner and his estranged wife, Huma Abedin, a top aide to Mrs. Clinton, federal law enforcement officials said Friday. The F.B.I. is investigating illicit text messages that Mr. Weiner, a former Democratic congressman from New York, sent to a 15-year-old girl in North Carolina. The bureau told Congress on Friday that it had uncovered new emails related to the Clinton case — one federal official said they numbered in the thousands — potentially reigniting an issue that has weighed on the presidential campaign and offering a lifeline to Donald J. Trump less than two weeks before the election. In a letter to Congress, the F.B.I. director, James B. Comey, said that emails…