HANOI — Vietnam will showcase locally made weapons at an international arms fair in Hanoi on Thursday, as it seeks to boost its domestic industry and possibly export military equipment. Among the nearly 250 exhibitors will be top defense companies, including from the United States, Europe, Turkey and countries at war with each other, such as Israel, Iran, Russia and Ukraine. The Southeast Asian nation is a major importer of weapons, especially from Russia, having invested for years in its defense capabilities in an unstable region where it has clashed with China over boundaries in the South China Sea. But