In his Georgetown office that Friday in October 2018 Patrick Ewing — who recently revealed he’d been treated for COVID-19 — reiterated what he’d said on the night of Feb. 28, 2003, at Madison Square Garden, when his number, 33, was officially lifted to the Garden rafters, taking its proper place among the franchise giants. “I’m a Knick,” he said. “I’m always going to be a Knick.” Twenty years ago Tuesday, without knowing it, he said goodbye to that chapter of his life. He wishes it could have gone differently. He isn’t alone.