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

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 Additionally, a lot of unused/outdated rules were removed (`ExpandableListItem` and `SimpleIntegerPicker` cover most of these removed rules).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