“Bryan Fogel is an L.A.-based writer and amateur competitive bicyclist, co-author of a play about Jewish dating that enjoyed a long off-Broadway run and, quite possibly, the world’s luckiest first-time documentary filmmaker. That latter distinction is one of the attractions of Fogel’s “Icarus,” a happy-accident documentary that began as a lark and turned into a sometimes stunning look at Fogel’s friendship with the man who oversaw — then blew the whistle on — Russia’s far-reaching sports doping program.”