ENH: provide MPI native minOp, maxOp reduce multiple values

- consistent with sumOp

ENH: globalIndex with gatherNonLocal tag, and use leading dispatch tags

- useful for gather/write where the master data can be written
 separately.  Leading vs trailing dispatch tags for more similarity to
 other C++ conventions.

applications/utilities/postProcessing/lagrangian/particleTracks/particleTracksSampler.H

@@ -144,7 +144,7 @@ public:
 
         void resetCloud(const label localCloudSize)
         {
-            cloudGather_.reset(localCloudSize, globalIndex::gatherOnly{});
+            cloudGather_.reset(globalIndex::gatherOnly{}, localCloudSize);
             origParcelIds_.resize_nocopy(localCloudSize);
             origProcIds_.resize_nocopy(localCloudSize);
         }