Instead of having a separate iterator for variants, we can now do this:

auto variant_values = input.Values<VectorVariantType>();

for (idx_t r = 0; r < count; r++) {
    auto entry = variant_values[r];
    if (entry.IsNull()) {
        // top level variant is NULL
    }
    auto val = entry.GetValue(); // get the variant value
}

Also, for clarity, renamed:

• VariantIteratorState -> VariantIterator - this represents the iterator over the variant vector that holds the unified vector formats, etc - created once per vector
• VariantIterator -> VariantNode - this is a single node within the variant (e.g. an integer, an object, etc)

CC @Tishj