Rob asked me to back out GENERATED_*_BODY -> GENERATED_BODY change for now until the "_Validate and _Implementation auto-generation" discussion is over.
#codereview Robert.Manuszewski
[CL 2481343 by Jaroslaw Palczynski in Main branch]
Added Shared link to base class and override excerpt name in MaterialGraphNode so that it can associate documentation with the MaterialExpression type
[CL 2231476 by Matthew Griffin in Main branch]