default Timers.Finishable startStage(String name) {
    return startStage(name, true);
  }
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}.
planetiler-core/src/main/java/com/onthegomap/planetiler/stats/Stats.java