BHV-4060: Trigger reflow when picker is opened.

Issue
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The content of the picker when a `moon.ExpandableIntegerPicker` is expanded is empty. This is caused by a regression from a fix for BHV-737 that prevented `resized`, and effectively `reflow`, from being called when the picker is expanded.

Fix
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We trigger a reflow of the picker whenever it is opened.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>