BUG: Support legacy .dream3d files in OOC backfill

backfillReadOnlyOocStores hardcoded "DataStructure" as the root HDF5
group name. Legacy DREAM3D 6.5/6.6 files use "DataContainers" instead.
Fall back to "DataContainers" when "DataStructure" is not found.

Author: joeykleingers

src/simplnx/Filter/Actions/ImportH5ObjectPathsAction.cpp

@@ -60,10 +60,17 @@ Result<> backfillReadOnlyOocStores(DataStructure& dataStructure, const std::vect
     return {};
   }
 
-  auto dsGroup = fileReader.openGroup("DataStructure");
+  // Support both NX format ("DataStructure") and legacy DREAM3D 6.5/6.6 format ("DataContainers")
+  std::string rootGroupName = "DataStructure";
+  auto dsGroup = fileReader.openGroup(rootGroupName);
   if(!dsGroup.isValid())
   {
-    return MakeErrorResult(-6210, "backfillReadOnlyOocStores: No 'DataStructure' group in HDF5 file");
+    rootGroupName = "DataContainers";
+    dsGroup = fileReader.openGroup(rootGroupName);
+    if(!dsGroup.isValid())
+    {
+      return MakeErrorResult(-6210, "backfillReadOnlyOocStores: No 'DataStructure' or 'DataContainers' group in HDF5 file");
+    }
   }
 
   const auto filePath = fileReader.getFilePath();
@@ -144,7 +151,7 @@ Result<> backfillReadOnlyOocStores(DataStructure& dataStructure, const std::vect
       auto dataset = currentGroup->openDataset(pathComponents.back());
       auto chunkDims = dataset.getChunkDimensions();
 
-      std::string hdf5Path = "DataStructure/" + childPath.toString();
+      std::string hdf5Path = rootGroupName + "/" + childPath.toString();
       auto tupleShape = iDataStore->getTupleShape();
       auto componentShape = iDataStore->getComponentShape();