Fix preview position in 2D previews

Turn off pixel caching for nodes

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/MaterialGraphPreviewGenerator.cs

 
             Mesh previewMesh = mesh == null ? s_Meshes[0] : mesh;
 
-            Vector3 previewPosition = -previewMesh.bounds.center;
+            Vector3 previewPosition = previewMesh.bounds.center;
 
             Graphics.DrawMesh(
                 mode == PreviewMode.Preview3D ? previewMesh : quad,

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialNodeView.cs

                 UpdateSize();
             }
 
-            clippingOptions = ClippingOptions.ClipContents;
+            mainContainer.clippingOptions = ClippingOptions.ClipContents;
         }
 
         public AbstractMaterialNode node { get; private set; }