Though there’s little optimism in the content or title of My Undesirable Friends, the staggering two-part documentary from Julia Loktev, the steel spine holding its twelve hours together is an unshakable shared sense of purpose. The massive monument to journalism, competing in length and ambition with legendary feats of nonfiction like Shoah and the Up series, necessarily expands its scope in its six-hour back half, My Undesirable Friends: Part …