ENH: chemFoam - updated mesh creation

applications/solvers/combustion/chemFoam/createSingleCellMesh.H

 Info<< "Constructing single cell mesh" << nl << endl;
 
-pointField points(8);
-points[0] = vector(0, 0, 0);
-points[1] = vector(1, 0, 0);
-points[2] = vector(1, 1, 0);
-points[3] = vector(0, 1, 0);
-points[4] = vector(0, 0, 1);
-points[5] = vector(1, 0, 1);
-points[6] = vector(1, 1, 1);
-points[7] = vector(0, 1, 1);
-
-faceList faces = cellModel::ref(cellModel::HEX).modelFaces();
-
-fvMesh mesh
-(
-    IOobject
-    (
-        fvMesh::defaultRegion,
-        runTime.timeName(),
-        runTime,
-        IOobject::READ_IF_PRESENT
-    ),
-    std::move(points),
-    std::move(faces),
-    labelList(6, Zero), // owner
-    labelList()         // neighbour
-);
-
-List<polyPatch*> patches(1);
-
-patches[0] = new emptyPolyPatch
-(
-    "boundary",
-    6,
-    0,
-    0,
-    mesh.boundaryMesh(),
-    emptyPolyPatch::typeName
-);
-
-mesh.addFvPatches(patches);
+autoPtr<fvMesh> meshPtr = dummyFvMesh::singleCellMesh(runTime);
+fvMesh& mesh = meshPtr();