GHSA-gfgm-chr3-x6px

In function `Table::as_ref`, a reference of vector is force cast to slice. There are multiple problems here: 1. To guarantee the size is correct, we have to first do `Vec::shrink_to_fit`. The function requires a mutable reference, so we have to force cast from immutable to mutable, which is undefined behavior (UB). 2. Even if (1) is sound, `&Vec<T>` and `&[T]` still might not have the same layout. Treating them equally may lead to undefinted behavior (UB).