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/postProcessing/dataConversion/foamToEnsightParts/findFields.H

@@ -103,9 +103,9 @@ if (timeDirs.size())
             fileName::FILE
         );
 
-        forAll(contents, fileI)
+        for (const fileName& file : contents)
         {
-            missing.erase(contents[fileI].name());
+            missing.erase(file.name());
         }
 
         volumeFields.erase(missing);

applications/utilities/postProcessing/graphics/PVReaders/vtkPVFoam/vtkPVFoamUpdateInfo.C

@@ -227,7 +227,7 @@ void Foam::vtkPVFoam::updateInfoLagrangian
 
     for (const instant& t : dbPtr_().times())
     {
-        names.insert
+        names.insertMany
         (
             readDir
             (