mapFields, mapFieldsPar: Removed the subtract option and supporting complexity in meshToMesh0 and meshToMesh

The subtract option in mapFieldsPar was not implemented correctly and the
significant complexity in meshToMesh required to support it creates an
unwarranted maintenance overhead.  The equivalent functionality is now provided
by the more flexible, convenient and simpler subtract functionObject.

applications/utilities/preProcessing/mapFields/MapConsistentVolFields.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2021 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2022 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -35,13 +35,12 @@ License
 namespace Foam
 {
 
-template<class Type, class CombineOp>
+template<class Type>
 void MapConsistentVolFields
 (
     const IOobjectList& objects,
     const meshToMesh0& meshToMesh0Interp,
-    const meshToMesh0::order& mapOrder,
-    const CombineOp& cop
+    const meshToMesh0::order& mapOrder
 )
 {
     typedef GeometricField<Type, fvPatchField, volMesh> fieldType;
@@ -78,12 +77,11 @@ void MapConsistentVolFields
             );
 
             // Interpolate field
-            meshToMesh0Interp.interpolate
+            meshToMesh0Interp.interpolate<Type>
             (
                 fieldTarget,
                 fieldSource,
-                mapOrder,
-                cop
+                mapOrder
             );
 
             // Write field
@@ -100,8 +98,7 @@ void MapConsistentVolFields
                 meshToMesh0Interp.interpolate
                 (
                     fieldSource,
-                    mapOrder,
-                    cop
+                    mapOrder
                 )
             );