ALGIERS (Reuters) - North African heavyweight Algeria is worried by the chaos in neighboring Mali, where Islamist militants have seized vast tracts of the country, but believes foreign intervention will only make things worse. Much is at stake for Algeria, Africa's biggest country and a wealthy oil and gas exporter that shares a 2,000 km (1,250 mile) border with Mali and sees itself as a major regional power. It is still recovering from its own conflict with armed Islamists in which international human rights groups say more than 200,000 people were killed over two decades. ...