Despite the official launch being a full week away, the first third-generation iPad pre-orders have started to ship from Apple’s assembly partner Foxconn. 9to5Mac’s Seth Weintraub reports that one of his pre-orders—a 16GB Wi-Fi unit with engraving—has shipped from Chengdu in Western China. As noted in the report, Chengdu was the site of an explosion at an iPad 2 production line run by Foxconn. The shipment notification, as…