* Renames for 2D and 3D
* Class name was confusing, given both 2D and 3D have a "visible" property that is unrelated to actual on-screen visibility.
* New name makes it clear that this is about visibility on screen.
More saturated icons go better with the new editor theme.
These color changes only apply when using a dark theme.
The editor icon saturation can still be adjusted in the Editor Settings.
Setting the editor icon saturation setting to 0.77 should roughly match
the old icon saturation.