Cuberille: BUG: Failure Case with QEMesh

The `Cuberille` module was ingested into ITK from the (now archived) `ITKCuberille` remote module. This issue tracks, in ITK proper, the work originally filed as **InsightSoftwareConsortium/ITKCuberille#66** by @sudomakeinstall (2020-10-22).

---

Imagine an image with only two foreground pixels, offset by `{1, 1, 0}`. When extracting the surface of this image as a mesh, it is necessary to duplicate the coincident edge, creating two disconnected cubes, in order to ensure that the result is manifold. A slice through the z plane would show:

```
*---*---*
| A | |
*---*---*
| | B |
*---*---*
```

Now imagine that these foreground pixels are still flanked by background pixels in the z plain, but are "connected" into the same connected component by foreground pixels in the two adjacent z plains:

```
Z-1 Z Z+1
*---*---* *---*---* *---*---*
| X | X | | A | | | X | X |
*---*---* *---*---* *---*---*
| | X | | | B | | | X |
*---*---* *---*---* *---*---*
```
Here, the coincident edge of pixels `A` and `B` must again be duplicated; but unlike the first example, the two distinct edges actually connect *the same two vertices*. Quite reasonably, when asked to create a face which would require an edge between two vertices, `itk::QuadEdgeMesh` checks [1] to see whether there is an existing edge, and refuses to create a new edge if one already exists:
```
QEPrimal * edge = this->FindEdge(pid0, pid1);

if (edge)
{
if (edge->IsLeftSet())
{
itkDebugMacro("Edge [" << i << " " << ((i + 1) % N) << " has a left face.");
return (QEPrimal *)nullptr;
}
}
}
```
Most of the time, this is what we want--but in the case described above, it acts as a bug. It's not immediately obvious to me how to detect when this check is and is not necessary; as I work through this problem, I thought I would post it as an issue in case anyone else had any insight--pun intended. ;-D

[1] https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/Core/QuadEdgeMesh/include/itkQuadEdgeMesh.hxx#L1211-L1221

Here's a MCE demonstrating the issue:

```cpp
#include
#include
#include
#include

const unsigned int Dimension = 3;
using TPixel = unsigned char;
using TImage = itk::Image< TPixel, Dimension >;
//using TMesh = itk::Mesh;
using TMesh = itk::QuadEdgeMesh;
using TExtract = itk::CuberilleImageToMeshFilter< TImage, TMesh >;
using TMeshWriter = itk::MeshFileWriter< TMesh >;

int main(int argc, char** argv)
{

const auto image = TImage::New();
TImage::RegionType region({{0,0,0}}, {{5,4,4}});
image->SetBufferedRegion(region);
image->Allocate();
image->FillBuffer(0);

image->SetPixel({{1, 1, 1}}, 1); // A
image->SetPixel({{2, 1, 1}}, 1); // B
image->SetPixel({{3, 1, 1}}, 1); // C
image->SetPixel({{1, 2, 1}}, 1); // D
image->SetPixel({{3, 2, 1}}, 1); // E

image->SetPixel({{1, 2, 2}}, 1); // F
image->SetPixel({{2, 2, 2}}, 1); // G
image->SetPixel({{3, 2, 2}}, 1); // H

const auto extract = TExtract::New();
extract->SetInput( image );
extract->SavePixelAsCellDataOn();
extract->GenerateTriangleFacesOff();
extract->ProjectVerticesToIsoSurfaceOff();

const auto m_writer = TMeshWriter::New();
m_writer->SetInput( extract->GetOutput() );
m_writer->SetFileName( "mesh.obj" );
m_writer->Update();

const auto n_cell = extract->GetOutput()->GetNumberOfCells();
const auto n_data = extract->GetOutput()->GetCellData()->Size();

if (n_cell != n_data) {
std::cout << "This fails if using itk::QuadEdgeMesh." << std::endl;
std::cout << "n_cell: " << n_cell << std::endl;
std::cout << "n_data: " << n_data << std::endl;
return EXIT_FAILURE;
}

std::cout << "This succeeds if using itk::Mesh." << std::endl;

return EXIT_SUCCESS;

}
```

---

Original report: https://github.com/InsightSoftwareConsortium/ITKCuberille/issues/66 (archived repository). Credit: @sudomakeinstall.