BHV-15258: When @moon-checkbox-icon-width: 32, horizontal scroller does not appear

### Issue:
checkbox icon was overflowing the item dimensions and causing a scroller to appear
### Fix:
reduce the dimensions of the tap area for the checkbox icon, remove the width attribute of the checkbox and let it auto-size, adjust the position of the icon in checkbox item

Enyo-DCO-1.1-Signed-off-by: Krishna Rangarajan <krishna.rangarajan@lge.com>