New sound output test design

This PR implements the new output test window as defined in the mockups in #2046.

Missing things:

• Update subwoofer icon
• Add missing icons for "front_left_of_center" and "front_right_of_center"
• Add handling for mono audio (I need a design for that)

Fixes #1305 (closed), #1315 (closed) and #1726 (closed).

Before

After

Complex