Add data_type to SubItemValuePerItem and SubItemValuePerItem::SubView

This allows to use ArrayUtils method on their instances

src/mesh/SubItemValuePerItem.hpp

@@ -27,6 +27,9 @@ class SubItemValuePerItem<DataType,
  public:
   static const ItemType item_t{item_type};
   static const ItemType sub_item_t{sub_item_type};
+
+  using data_type = DataType;
+
  private:
   bool m_is_built{false};
 
@@ -41,9 +44,13 @@ class SubItemValuePerItem<DataType,
  public:
   class SubView
   {
+   public:
+    using data_type = DataType;
+
    private:
     KOKKOS_RESTRICT DataType* const m_sub_values;
     const size_t m_size;
+
    public:
     KOKKOS_INLINE_FUNCTION
     const DataType& operator[](const size_t& i) const