[macOS] Visual Artifacts When Toast Is Active

[vkhitrin]

(Tested on https://github.com/pop-os/libcosmic?rev=953685a88267894ea3fa40f2b99139c3c4e784d6#953685a88267894ea3fa40f2b99139c3c4e784d6)
(Observed at vkhitrin/cosmicding#30)

I have observed a scenario that in some cases, when a toast notification becomes active, visual artifacts appear.
In the recording below, the artifacts appear once a toast notification is raised, and the artifacts themselves looks like the trailing icon of widget::button::link.

screencapture.mov

[vkhitrin]

Once I have added icons to macOS, the visual artifacts are more severe.

The artifacts can also appear in the following scenario:

• Opening a menu that contains widget::menu::MenuItem::CheckBox (icons are not rendered, refer to [macOS] Icons From Builtin Widgets With Icons Using widget::icon::from_name() Do Not Render #763)

macos_libcosmic_additional_visual_artifacts.mp4