Use succinctMillis to print task running time (facebookincubator#10683)

Summary:
`succinctMillis` will help unify time unit.

Pull Request resolved: facebookincubator#10683

Reviewed By: kagamiori

Differential Revision: D60903986

Pulled By: xiaoxmeng

fbshipit-source-id: 5856064b3f03c7665650eb448b2bc4ef65542f21

velox/exec/Task.cpp

@@ -1140,8 +1140,8 @@ void Task::removeDriver(std::shared_ptr<Task> self, Driver* driver) {
     if (self->numFinishedDrivers_ == self->numTotalDrivers_) {
       LOG(INFO) << "All drivers (" << self->numFinishedDrivers_
                 << ") finished for task " << self->taskId()
-                << " after running for " << self->timeSinceStartMsLocked()
-                << " ms.";
+                << " after running for "
+                << succinctMillis(self->timeSinceStartMsLocked());
     }
   }
   stateChangeNotifier.notify();
@@ -1880,7 +1880,7 @@ ContinueFuture Task::terminate(TaskState terminalState) {
 
     LOG(INFO) << "Terminating task " << taskId() << " with state "
               << taskStateString(state_) << " after running for "
-              << timeSinceStartMsLocked() << " ms.";
+              << succinctMillis(timeSinceStartMsLocked());
 
     taskCompletionNotifier.activate(
         std::move(taskCompletionPromises_), [&]() { onTaskCompletion(); });