Use color extraction for arrow popup.

- Updated logic to accept any view that is a a child of draglayer
  (from being workspace dependent)
- Move color extraction logic from widget class to utility class.
- Initial CL, future CL will interpolate between colors
  and expand color extraction to other abstract floating views.

Bug: 175329686
Test: long press on colorful wallpaper and test colors are extracted
      test in multiwindow mode
Change-Id: I18a6bb5013de4eea7e9b45810401f5b9b3cd7302