zerovec-derive incorrectly uses `#[repr(packed)]`
The affected versions make unsafe memory accesses under the assumption that #[repr(packed)] has a guaranteed field order. The Rust specification does not guarantee this, and https://github.com/rust-lang/rust/pull/125360 (1.80.0-beta) starts reordering fields of #[repr(packed)] structs, leading to illegal memory accesses. The patched versions 0.9.7 and 0.10.3 use #[repr(C, packed)], which guarantees field order.