tabbox: Reset tabbox when compositing is toggled on Wayland
On Wayland, every internal window that uses OpenGL has a context that shares framebuffer objects with kwin's context.
When compositing is toggled, kwin's context will be destroyed and so internal windows no longer can pass their framebuffer objects to kwin.
At that point, QtQuick scene graph renderer must re-create the OpenGL context and all related resources, e.g. textures, etc.
Unfortunately, there is no any way to invalidate the scene graph externally.
In order to work around this issue, we can reset the tabbox when compositing gets toggled similar to how the outline visual handles this corner case.