HDRenderPipeline: Add material definition for research scientist

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Material.hlsl

 #include "Lit/Lit.hlsl"
 #elif defined(UNITY_MATERIAL_UNLIT)
 #include "Unlit/Unlit.hlsl"
+#elif defined(UNITY_MATERIAL_IRIDESCENCE)
+#include "Iridescence/Iridescence.hlsl"
 #endif
 
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