I've taken a quick look and left some suggestions on how to simplify this, in particular separating the concatenation of the list values and the list offsets will result in less code, require less codegen, and likely perform better.

i.e. something like (not tested)

DataType::List(f) => {
    let values: Vec<_> = arrays.iter().map(|x| x.as_list::<i32>().values()).collect();
    let new_values = concat(&values)?;
    let offsets = OffsetBuffer::from_lengths(
        arrays.iter().flat_map(|x| x.as_list::<i32>().offsets()
             .windows(2).map(|w| w[1].as_usize() - w[0].as_usize()))
    );
    let nulls = ...
    ListArray::new(f, offsets, new_values, nulls)
}

This is looking very promising, just a small comment r.e. avoiding ArrayData

I'll try to find some time for a more thorough review in the next few days if nobody else gets there first