fixing shader compilation error and renaming define for fb fetch idx

Author: jonuuukas

com.unity.render-pipelines.universal/Editor/Decal/DecalPass.template

@@ -64,8 +64,8 @@ Pass
     float4 _SelectionID;
     #endif
     #if _RENDER_PASS_ENABLED
-    #define DEPTH_COPY 0
-    FRAMEBUFFER_INPUT_FLOAT(DEPTH_COPY);
+    #define GBUFFER3 0
+    FRAMEBUFFER_INPUT_HALF(GBUFFER3);
     #endif
     // Includes
     $splice(PreGraphIncludes)

com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/ShaderPassDecal.hlsl

@@ -182,13 +182,13 @@ void Frag(PackedVaryings packedInput,
 #if defined(DECAL_PROJECTOR)
 #if UNITY_REVERSED_Z
 #if _RENDER_PASS_ENABLED
-    float depth = LOAD_FRAMEBUFFER_INPUT(DEPTH_COPY, input.positionCS.xy);
+    float depth = LOAD_FRAMEBUFFER_INPUT(GBUFFER3, input.positionCS.xy);
 #else
     float depth = LoadSceneDepth(input.positionCS.xy);
 #endif
 #else
 #if _RENDER_PASS_ENABLED
-    float depth = lerp(UNITY_NEAR_CLIP_VALUE, 1, LOAD_FRAMEBUFFER_INPUT(DEPTH_COPY, input.positionCS.xy));
+    float depth = lerp(UNITY_NEAR_CLIP_VALUE, 1, LOAD_FRAMEBUFFER_INPUT(GBUFFER3, input.positionCS.xy));
 #else
     // Adjust z to match NDC for OpenGL
     float depth = lerp(UNITY_NEAR_CLIP_VALUE, 1, LoadSceneDepth(input.positionCS.xy));