BHV-19184: Prevent pointer events from IntegerPicker's client area.

### Issue
In `moon.IntegerPicker` controls, tapping the client area while the control was scrolling to a value would interrupt the scroll animation and could potentially leave the currently displayed value in an undesired position.

### Fix
We use the `pointer-events:none` CSS rule.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>