Arithmetic with scalars doesn't work on slices

[bjchambers]

Describe the bug

As in #738 and #740, modulus_scalar and divide_scalar don't work on slices.

To Reproduce

    #[test]
    fn test_primitive_array_modulus_scalar_sliced() {
        let a = Int32Array::from(vec![Some(15), None, Some(9), Some(8), None]);
        let a = a.slice(1, 4);
        let a = as_primitive_array(&a);
        let actual = modulus_scalar(a, 3).unwrap();
        let expected = Int32Array::from(vec![None, Some(0), Some(2), None]);
        assert_eq!(actual, expected);
    }

Expected behavior
The test succeeds.

Actual behavior
The test doesn't succeed.

Additional context

[alamb]

Wow -- thank you for the train of fixes @bjchambers