A long-dormant and formerly contaminated site in Sayreville, once home to gunpowder and chemical plants, is finding new life under a development that will add more than a million square feet of modern industrial space to the market in Central Jersey. The three-building Arsenal Trade Center also promises to bring new jobs and ratables to the Raritan Bay region. Experts say that, while players like Amazon are stepping back from warehouse and logistics expansion in the state, the market for such properties remains robust.