GeometricField: Renamed internalField() -> primitiveField() and dimensionedInternalField() -> internalField()

These new names are more consistent and logical because:

primitiveField():
primitiveFieldRef():
    Provides low-level access to the Field<Type> (primitive field)
    without dimension or mesh-consistency checking.  This should only be
    used in the low-level functions where dimensional consistency is
    ensured by careful programming and computational efficiency is
    paramount.

internalField():
internalFieldRef():
    Provides access to the DimensionedField<Type, GeoMesh> of values on
    the internal mesh-type for which the GeometricField is defined and
    supports dimension and checking and mesh-consistency checking.

applications/utilities/postProcessing/dataConversion/foamToTetDualMesh/foamToTetDualMesh.C

@@ -91,7 +91,7 @@ void ReadAndMapFields
             )
         );
 
-        Field<Type>& fld = tetFields[i].internalFieldRef();
+        Field<Type>& fld = tetFields[i].primitiveFieldRef();
 
         // Map from read field. Set unmapped entries to nullValue.
         fld.setSize(map.size(), nullValue);