Remove I3DEngine CryCommon Interface (#567)

Delete:

- I3DEngine
- Missions
- Time of day
- GameEffectsSystem Gem
- ImageProcessing Gem
- SVOGI Gem
- Various other things that don't do anything now that the legacy renderer has been removed.

Code/Sandbox/Editor/DisplaySettings.cpp

@@ -86,11 +86,6 @@ void CDisplaySettings::PostInitApply()
 void CDisplaySettings::SetRenderFlags(int flags)
 {
     m_renderFlags = flags;
-
-    if (!GetIEditor()->Get3DEngine())
-    {
-        return;
-    }
 }
 
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