A Chinese national flag outside the Beijing No. 2 Intermediate People's Court in Beijing, China, March 31, 2022. Mark R. Cristino, EPA-EFE/File TOKYO — China is considering banning the export of technologies used to produce high-performing rare earth magnets, which are crucial for powering products from electric vehicles to mobile phones, a proposed revision to its export control measures showed Wednesday. As the United States tightens its grip on semiconductor technologies, also crucial for high-tech products, China, a major producer of some rare earth minerals, is apparently trying to dominate industries where it already has a large market share and…