[Port] [6000.0] [UUM-78849] Add an option to include Custom Function Node source using #include_with_pragmas

https://jira.unity3d.com/browse/UUM-78849

This PR addresses the issue by:
- Defaulting the behavior to `#include_with_pragmas` to restore Shader Graph's previous behavior
- Adding a toggle to choose between `#include` and `#include_with_pragmas` on Custom Function Nodes

Author: svc-reach-platform-support

Packages/com.unity.shadergraph/Editor/Data/Nodes/Utility/CustomFunctionNode.cs

@@ -124,6 +124,15 @@ public string functionSource
             set => m_FunctionSource = value;
         }
 
+        [SerializeField]
+        private bool m_FunctionSourceUsePragmas = true;
+
+        public bool functionSourceUsePragmas
+        {
+            get => m_FunctionSourceUsePragmas;
+            set => m_FunctionSourceUsePragmas = value;
+        }
+
         [SerializeField]
         string m_FunctionBody = k_DefaultFunctionBody;
 
@@ -264,7 +273,7 @@ public void GenerateNodeFunction(FunctionRegistry registry, GenerationMode gener
                     if (string.IsNullOrEmpty(path))
                         path = functionSource;
 
-                    registry.RequiresIncludePath(path);
+                    registry.RequiresIncludePath(path, shouldIncludeWithPragmas: functionSourceUsePragmas);
                     break;
                 case HlslSourceType.String:
                     registry.ProvideFunction(hlslFunctionName, builder =>

Packages/com.unity.shadergraph/Editor/Drawing/Views/HlslFunctionView.cs

@@ -15,6 +15,7 @@ internal class HlslFunctionView : VisualElement
         private EnumField m_Type;
         private TextField m_FunctionName;
         private ObjectField m_FunctionSource;
+        private Toggle m_FunctionSourceUsePragmas;
         private TextField m_FunctionBody;
 
         internal HlslFunctionView(CustomFunctionNode node)
@@ -85,6 +86,21 @@ private void Draw(CustomFunctionNode node)
                 }
             });
 
+            m_FunctionSourceUsePragmas = new Toggle
+            {
+                value = node.functionSourceUsePragmas
+            };
+            m_FunctionSourceUsePragmas.RegisterValueChangedCallback(s =>
+            {
+                if (s.newValue != node.functionSourceUsePragmas)
+                {
+                    node.owner.owner.RegisterCompleteObjectUndo("Change Function Source Pragma Usage");
+                    node.functionSourceUsePragmas = s.newValue;
+                    node.ValidateNode();
+                    node.Dirty(ModificationScope.Graph);
+                }
+            });
+
             m_FunctionBody = new TextField { value = node.functionBody, multiline = true };
             m_FunctionBody.AddToClassList("sg-hlsl-function-view__body");
             m_FunctionBody.verticalScrollerVisibility = ScrollerVisibility.Auto;
@@ -133,6 +149,15 @@ private void Draw(CustomFunctionNode node)
                         sourceRow.Add(m_FunctionSource);
                     }
                     Add(sourceRow);
+
+                    VisualElement functionSourceUsePragmasRow = new VisualElement() { name = "Row" };
+                    {
+                        functionSourceUsePragmasRow.Add(new Label("Use Pragmas"));
+                        functionSourceUsePragmasRow.Add(m_FunctionSourceUsePragmas);
+                        functionSourceUsePragmasRow.tooltip = "Determines whether or not Unity pragmas from the included file will be used in the generated shader.";
+                    }
+                    Add(functionSourceUsePragmasRow);
+
                     break;
                 case HlslSourceType.String:
                     VisualElement bodyRow = new VisualElement() { name = "Row" };