Improved keyboarding behaviors for lists

[YuliKl]

Some components don't have appropriate focus visuals and keyboarding behaviors when they receive keyboard focus. This issue is tracking using the onKeyDown, onKeyUp events to implement the right behaviors for lists and popups based on Keyboarding interactions guidance document for Windows.

• FlatList - Focus rect is drawn around the entire component
• FlatList - User can't move focus to a specific item using arrow keys

Related to #3006

[ahimberg]

The outer focus rect is coming from the scrollview which currently defaults to being a tabstop (that was to workaround an issue where clicking on anything in a scrollview would move focus to the first keyfocusable child). should revisit that

since flatlist is just a scrollview with random children it is not getting any list item behaviors