The first three fall film festivals have come and gone, with hundreds of films and dozens of Oscars contenders unveiling for movie fans in Venice, Telluride and Toronto. And after all those screenings over 19 days from late August through mid September, who got the biggest Oscar-season boost? Would you believe Christopher Nolan and Steven Spielberg? Mind you, neither Nolan nor Spielberg debuted a film in Venice, Telluride or Toronto. Nolan’s “Dunkirk” opened in late July, and while he screened “Dunkirk” in Toronto as part of a tribute to the 50th anniversary of IMAX, the movie was a known quantity long.