A generation ago, George Clooney worked with Brad Pitt in Vegas on a heist, in 2001, for director Steven Soderbergh’s remake of “Ocean’s Eleven.” People went to theaters to see it, and lives were not changed, merely entertained for a couple of hours — though who knows, really? Thanks to ensemble ringers Carl Reiner and Elliott Gould, exemplars of an earlier, better-trained show business tradition, maybe a few moviegoers’ lives were changed, subtly, simply by watching the legendary pros strolling through, delivering their eccentric characterizations on a level of rare, blithe confidence unknown…