@Override
      public ProcessTime elapsed() {
        return timer.elapsed();
      }
Records that a long-running task with {@code name} has started and returns a handle to call when finished.
<p>
Also sets the "stage" prefix that shows up in the logs to {@code name} if {@code log} is true.
planetiler-core/src/main/java/com/onthegomap/planetiler/stats/Stats.java