CHRISTCHURCH, New Zealand — Once reliant on aging, second-hand vessels from the United States, a steady drumbeat of new warships is beginning to enter Philippine Navy service. The new capabilities are part of a rapid modernization program there, prompted by aggressive Chinese tactics and territorial claims in the adjacent South China Sea . The world’s largest shipbuilder, South Korea’s HD Hyundai Heavy Industries (HHI), is the primary supplier of these new vessels, and the latest warship to