BHV-1222: Add proper styling for expanded state, clean up cruft.

Issue
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The expanded state of the `ExpandableIntegerPicker` shows a caret oriented in the wrong direction.

Fix
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There was a lot of missing styling for the `ExpandableIntegerPicker` header, which has now been added. Additionally, a lot of unused/outdated rules were removed.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>