By Richard Cowan, David Morgan and Makini Brice WASHINGTON (Reuters) – Democrats and Republicans in the U.S. Senate headed off a prolonged impeachment trial for Donald Trump on Saturday with an agreement to enter into evidence details of the former president’s remarks in a call with a top Republican during the deadly Capitol riot. The agreement followed a chaotic vote to allow witnesses in the proceedings, which could have delayed a conclusion for weeks, heightened divisions and stymied efforts by President Joe Biden to move beyond the controversies of his predecessor. The Senate, Trump’s lawy…