ENH: consistency of HashSet setMany(), insertMany() with packed-list version

- this also provides a better separation of the intent
  (ie, inserting a single value, or inserting multiply values)

applications/utilities/mesh/manipulation/refineMesh/refineMesh.C

@@ -349,11 +349,7 @@ int main(int argc, char *argv[])
     forAll(oldToNew, oldCelli)
     {
         const labelList& added = oldToNew[oldCelli];
-
-        forAll(added, i)
-        {
-            newCells.insert(added[i]);
-        }
+        newCells.insertMany(added);
     }
 
     Info<< "Writing refined cells ("

applications/utilities/mesh/manipulation/splitMesh/regionSide.C

@@ -301,10 +301,7 @@ void Foam::regionSide::walkAllPointConnectedFaces
         const label facei = iter.key();
         const labelList& fEdges = mesh.faceEdges()[facei];
 
-        forAll(fEdges, fEdgeI)
-        {
-            regionEdges.insert(fEdges[fEdgeI]);
-        }
+        regionEdges.insertMany(fEdges);
     }