Aug 8 (Reuters) - Degrowth - the idea that a finite planet cannot sustain ever-increasing consumption - is about the closest you can get to a heresy in economics, where growth is widely held as the best route to prosperity. But, as climate change accelerates and supply chain disruptions offer rich-world consumers an unaccustomed taste of scarcity, the theory is becoming less taboo and some have started to ponder what a degrowth world might look like. After the U.N. climate science agency this year called for cuts in consumer demand - a core degrowth premise - the think tank that...