Fixes BHV-14474

## Issue
The correct spotlight events were not being handled to hide/show the scroll bars when focus left via 5-way.

## Fix
Handle onSpotlightFocused and onSpotlightBlur events in moon.ScrollStrategy and remove related cruft from moon.Scroller

## Notes
Relies on changes in CMB-1706 to move spotlight container back to Scroller from viewport (PR #1618)

Enyo-DCO-1.1-Signed-off-by: Ryan Duffy <ryan.duffy@lge.com>