feature/il_partition_matset_support (#898)

* Add initial element-dominant matset support

WIP, bug in uni-buffer support

* Debugging index issue

* Fix support for material based uni buffer

* Add a unit test for material based uni buffers

* Add support for each type of matset

* Add some setup code for matset::combine

* Add support for combining matsets

* Iterate volume fraction data properly

* Add baselines for matset partition/combine

Some small code cleanup too

* Add unit test for different topology types

* Fix iteration bug

The way the o2m iterator was being used caused to fail to iterate
domains with only 1 element.

* Add spiral with matset unit test

* Add a test case with matset on domain 4

* Use common is_multi_buffer function

* Find o2m data_paths instead of guessing

src/libs/blueprint/conduit_blueprint_mesh_matset_xforms.cpp

@@ -125,16 +125,28 @@ to_silo(const conduit::Node &field,
     index_t matset_num_elems = 0;
     if(mset_is_matdom)
     {
-        NodeConstIterator eids_iter = matset["element_ids"].children();
-        while(eids_iter.has_next())
+        if(mset_is_unibuffer)
+        {
+            const DataAccessor<index_t> eids = matset["element_ids"].value();
+            const index_t N = eids.number_of_elements();
+            for(index_t i = 0; i < N; i++)
+            {
+                matset_num_elems = std::max(matset_num_elems, eids[i] + 1);
+            }
+        }
+        else
         {
-            const Node &eids_node = eids_iter.next();
-            const DataType eids_dtype(eids_node.dtype().id(), 1);
-            for(index_t ei = 0; ei < eids_node.dtype().number_of_elements(); ei++)
+            NodeConstIterator eids_iter = matset["element_ids"].children();
+            while(eids_iter.has_next())
             {
-                temp.set_external(eids_dtype, (void*)eids_node.element_ptr(ei));
-                const index_t elem_index = temp.to_int();
-                matset_num_elems = std::max(matset_num_elems, elem_index + 1);
+                const Node &eids_node = eids_iter.next();
+                const DataType eids_dtype(eids_node.dtype().id(), 1);
+                for(index_t ei = 0; ei < eids_node.dtype().number_of_elements(); ei++)
+                {
+                    temp.set_external(eids_dtype, (void*)eids_node.element_ptr(ei));
+                    const index_t elem_index = temp.to_int();
+                    matset_num_elems = std::max(matset_num_elems, elem_index + 1);
+                }
             }
         }
     }