ENH: fileHandler support for faMeshDistributor and field distributors

- fatten the interface to continue allowing write control with a bool
  or with a dedicated file handler. This may slim down in the future.

Co-authored-by: mattijs <mattijs>

applications/utilities/parallelProcessing/redistributePar/redistributePar.C

@@ -2622,7 +2622,8 @@ int main(int argc, char *argv[])
                 (
                     areaMeshPtr(),      // source
                     areaProcMeshPtr(),  // target
-                    faDistMap
+                    faDistMap,
+                    true                // isWriteProc (unused)
                 );
 
                 areaFields.redistributeAndWrite(distributor, true);