(This June 12 story refiles to clarify location in penultimate paragraph) By David Kirton SHENZHEN, China (Reuters) – David Fong made his way from a poor village in central China to the southern boomtown of Shenzhen as a young man in 1997. Over the next 25 years he worked for a succession of overseas manufacturers before building his own multi-million dollar business making everything from schoolbags to toothbrushes. Now 47, he has plans to branch out internationally by building internet-connected consumer devices. But after two years of coronavirus lockdowns that have pushed up the price of s…