Uninitialized memory exposure via trusted iterator length

Memory safety violation in the reorder Rust crate before 1.1.0 allows attackers to obtain uninitialized values through swap_index. swap_index trusts ExactSizeIterator::len(), sets a vector's length to that claim after yielding fewer elements, and returns initialized and uninitialized slots together. Reachability requires a consuming application to pass an iterator whose reported length exceeds its actual yield; safe Rust code can then read uninitialized process memory.