When using a mixed monochrome/colorful icon theme such as Breeze, we want widgets to always use monochrome icons for the icons in their CompactRepresentations, and at all Panel sizes.

In Plasma 5, this was accomplished by adding a monochrome icon to the Plasma theme that overrode the maybe-monochrome-maybe-colorful icon in the icon theme. But this did not work well because the colorful icon would still sometimes be substituted at larger sizes for which there was no monochrome icon in the Plasma theme.

This is solvable in Plasma 6 with our new "no icons in the Plasma theme" and "append -symbolic to always get a monochrome icon" world.

For each widget, we need to do two things
1. Make the widget ask for its icon using the "-symbolic" suffix
2. Ensure that there is a -symbolic monochrome version of that icon in the Breeze icon theme