Sept 29 (Reuters) - The founder of China Evergrande (3333.HK), the world's most indebted property developer, is being investigated for "illegal crimes", a fresh challenge for the tycoon and his embattled company as it struggles to stay afloat. Hui Ka Yan, 64, who founded Evergrande in 1996 in the southern Chinese province of Guangdong, is the latest tycoon to come under scrutiny since Chinese President Xi Jinping took power in 2012. Following is a list of some other high-profile Chinese executives who have been investigated or arrested under Xi's leadership. ZHAO WEIGUO, FORMER CHAIRMAN OF TSINGHUA UNIGROUP In March, the...