By Asif Shahzad and Syed Raza Hassan KARACHI, Pakistan (Reuters) – It was the kind of attack Pakistani authorities had dreaded. A highly educated female suicide bomber killed three Chinese teachers in Karachi in April along with their local driver, targeting nationals from Pakistan’s most important partner and seeking to undermine a relationship on which Islamabad’s financial survival largely depends. The blow threatened a major segment of Beijing’s Belt and Road infrastructure initiative, a $65 billion network of roads, railways, pipelines and ports in Pakistan that will connect China to the …