extra: Don't recurse in DList drop glue. #8295

The compiler-generated dtor for DList recurses deeply to drop Nodes.
For big lists this can overflow the stack.
auto merge of #8297 : brson/rust/dlist-dtor, r=brson

The compiler-generated dtor for DList recurses deeply to drop Nodes.
For big lists this can overflow the stack.

This is a problem for the new scheduler, where split stacks are not implemented.

Thanks @blake2-ppc