ENYO-373: Remove moon.Slider from set of pre-[initialized, rendered, destroyed] controls.

### Issue
We had made a change (https://github.com/enyojs/moonstone/pull/1729) to initialize, render, and destroy a select set of controls to improve load-time performance. Unfortunately, the inclusion of `moon.Slider` caused some unforeseen side-effects with WebKit, which resulted in some rendering discrepancies.

### Fix
`moon.Slider` is no longer included as part of this optimization.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>