StorageBasic allocation var type

AllocateBytes takes a vtkm::Id as the param. If vtkm::Id is an int32, this can lead to cases where there is enough memory but allocation fails because of integer overflow.

For example, say we have 200M vtkm::Vec<vtkm::Int32,4>s. This is a sizeof(vec) = 16, and 16 * 200M = overflow.

Is this a case we should handle? One suggestion would be to use a size_t instead of vtkm::Id when allocating.