Add tests and examples for UnionArray::from(data: ArrayData)

[HaoYang670]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
There is no test or example covering UnionArray::from(data: ArrayData). We need to add some.

impl From<ArrayData> for UnionArray {
    fn from(data: ArrayData) -> Self {
        let mut boxed_fields = vec![];
        for cd in data.child_data() {
            boxed_fields.push(make_array(cd.clone()));
        }
        Self { data, boxed_fields }
    }
}

[HaoYang670]

I have found the function is used in try_new which has been tested. So close this issue.