Support Temporal -> Utf8View casting #6734

    #[test]
    fn test_cast_timestamp_to_strings() {
        // "2018-12-25T00:00:02.001", "1997-05-19T00:00:03.005", None
        let array =
            TimestampMillisecondArray::from(vec![Some(864000003005), Some(1545696002001), None]);
        let out = cast(&array, &DataType::Utf8).unwrap();
        let out = out
            .as_any()
            .downcast_ref::<StringArray>()
            .unwrap()
            .into_iter()
            .collect::<Vec<_>>();
        assert_eq!(
            out,
            vec![
                Some("1997-05-19T00:00:03.005"),
                Some("2018-12-25T00:00:02.001"),
                None
            ]
        );
        let out = cast(&array, &DataType::LargeUtf8).unwrap();
        let out = out
            .as_any()
            .downcast_ref::<LargeStringArray>()
            .unwrap()
            .into_iter()
            .collect::<Vec<_>>();
        assert_eq!(
            out,
            vec![
                Some("1997-05-19T00:00:03.005"),
                Some("2018-12-25T00:00:02.001"),
                None
            ]
        );

        let out = cast(&array, &DataType::Utf8View).unwrap();
        let out = out
            .as_any()
            .downcast_ref::<StringViewArray>()
            .unwrap()
            .into_iter()
            .collect::<Vec<_>>();
        assert_eq!(
            out,
            vec![
                Some("1997-05-19T00:00:03.005"),
                Some("2018-12-25T00:00:02.001"),
                None
            ]
        );
    }