Owen Gleiberman Chief Film CriticIn “Alex Wheatle,” the fourth of Steve McQueen’s Small Axe films, we meet a young man who seems, quite literally, to have come from nothing. Alex (Sheyi Cole), born to Jamaican parents in 1963, was abandoned by his mother, and his father gave him over to the British social-services bureaucracy — which means that he grows up, in essence, as a Dickensian orphan.