[SHELVED] Material Layering Feedback for 4.19

The final shader should be very similar whichever method you use, the change is more in authoring the graph. When using Get/Set instead of Make/Break it generally gives you a smaller graph and will be better protected against potential future changes, e.g. new attributes can be added in later without having to re-connect an extra pin required by the Make/Break nodes. If you’re using “built-in” engine functions you shouldn’t need to worry.