Jem Aswad Senior Music EditorLike virtually every major rock act in the mid-1970s, the Rolling Stones had become bloated and overblown. After the generation-defining singles of the ‘60s and the stellar string of albums running from “Beggars Banquet” to “Exile on Main Street,” they’d eked out three comparatively uninspired sets that, due to Keith Richards’ formidable heroin addiction and its multiple accompanying legal problems, found Mick Jagger seeking musical foils in guitarist Mick Taylor and then guest keyboardist Billy Preston.