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/Include/IIconManager.h

@@ -61,7 +61,6 @@ struct IIconManager
     virtual IStatObj*   GetObject(EStatObject object) = 0;
     virtual int GetIconTexture(EIcon icon) = 0;
     virtual int GetIconTexture(const char* iconName) = 0;
-    virtual _smart_ptr<IMaterial> GetHelperMaterial() = 0;
     virtual QImage* GetIconBitmap(const char* filename, bool& haveAlpha, uint32 effects = 0) = 0;
     // Register an Icon for the specific command
     virtual void RegisterCommandIcon([[maybe_unused]] const char* filename, [[maybe_unused]] int nCommandId) {}