Donald Trump is so proud of a cognitive assessment he took while president that he boasted about it in a speech Saturday, while attacking what he claims is US President Joe Biden’s lack of mental acuity. The only problem: he then immediately got confused on the name of the doctor who oversaw the test. Trump extolled his powers of mental recall in a speech to hard-right allies in Detroit, challenging Biden to take the same cognitive exam he says he underwent in 2018 with then White House physician Ronny Jackson. However, he immediately flubbed the name of the former official, who is now one of …