Subtask of T7682: Proposed look-and-feel changes
https://bugs.kde.org/show_bug.cgi?id=384357

Most Breeze icons retain the visual design of the original--just with a little bit of flattening and bolder colors. But the Virtualbox icon is totally different, and obliterates the visual style of the original. This is fairly high-profile due to Virtualbox's popularity.