Add more education tips for widgets. (2/3)

Show education dialog on WidgetsFullSheet.
-Have a button in widget education dialog to intent into PixelTips apps.
-Make sure arrow tip view shows after dismissing education dialog on
WidgetsFullSheet if there is a widget to show it on.
-Update colors and layout for arrow tips.

Test: Tested manually
Bug: 185354491
Change-Id: I5cbdd02fc4f19a49a42dac4451b071e3d604747f