Apple Inc. has moved its self-driving car unit under the leadership of senior artificial intelligence executive John Giannandrea, who will oversee the company’s continued work on an autonomous system that could eventually be used in his own car. The project, known as Titan, is managed on a day-to-day basis by Doug Field. His team of hundreds of engineers have joined Giannandrea’s artificial intelligence and machine learning group, according to people familiar with the change. An Apple spokesperson declined to comment. Previously, Field reported to Bob Mansfield, Apple’s former senior vice…