With a Super Bowl ad, a massive Starbucks deal, and a public offering on the way, Oatly is suddenly everywhere. Just don’t call it milk. — Gastro-nomics is a column about the intersection of food, business, and culture. My initiation to Oatly, the Swedish alternative-milk darling, came in the storybook way that chief marketing officers dream about. The barista at my precious south Brooklyn neighborhood coffee shop recommended it back in 2018 as a way to…