PHILADELPHIA — Daylight on Wednesday revealed the destruction and devastation caused by an Amtrak train derailment in Philadelphia that left at least six people dead and injured dozens more, several critically, as survivors recalled a terrifying wreck that plunged them into darkness and chaos.Some passengers had to scramble through the windows of toppled cars to escape. One of the seven cars was completely mangled.The accident closed the nation’s busiest rail corridor between New York and Washington as federal …