There’s real pain in “A Real Pain,” and real pleasure, too. Jesse Eisenberg’s drama about a pair of cousins on a Holocaust tour through Poland premiered at this year’s Sundance Film Festival, which wrapped up its in-person and online screenings last month. It’s one of a handful of movies from the festival I watched virtually from the fest. Eisenberg, who wrote and directed the movie (it’s his second film, following 2022’s “When You Finish Saving the World”), stars as David Kaplan, a neurotic-to-the-core New Yorker who joins his cousin Benji (Kieran Culkin) on a guided tour through Poland, wher…