GHSA-jmwx-r3gq-qq3p vec-const attempts to construct a Vec from a pointer to a const slice

• crates.io vec-const: < 2.0.0 → fixed in 2.0.0

Affected versions of this crate claimed to construct a const `Vec` with nonzero length and capacity, but that cannot be done because such a `Vec` requires a pointer from an allocator. The implementation was later changed to just construct a `std::borrow::Cow`.