BHV-1368: Add wrapper div around ExpandableListItem header.

Issue
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In RTL mode, Webkit utilizes `padding-left` inconsistently when calculating `scrollWidth` for an element, causing text within a certain range (usually just beyond what can be displayed without a marquee) to not marquee.

Fix
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We bypass the use of padding for the `MarqueeItem` and instead wrap with a div that we apply padding to.

Notes
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In RTL mode, Webkit will ignore `padding-left` up to a certain point, returning a `scrollWidth` value that is either equal to the content width, the `clientWidth`, or the total horizontal padding, whichever is greater.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>