Molly Darlington/ReutersTwo British teenagers were convicted on Wednesday of the “frenzied and ferocious” murder of Brianna Ghey, a 16-year-old transgender girl who was stabbed more than 28 times at a park near Manchester in February. The pair, both 16 as well and identified only as Girl X and Boy Y, carefully planned Brianna’s killing and lied to cover up their crime. Both had a fascination with violence and torture, prosecutors said, with Girl X telling Boy Y she was “obsessed” with Brianna as