Ensure unique timestamps are generated for commit times with concurrent writers

public static String createNewInstantTime(long milliseconds) {
  return lastInstantTime.updateAndGet((oldVal) -> {
    String newCommitTime;
    do {
      newCommitTime = HoodieActiveTimeline.COMMIT_FORMATTER.format(new Date(System.currentTimeMillis() + milliseconds));
    } while (HoodieTimeline.compareTimestamps(newCommitTime, LESSER_THAN_OR_EQUALS, oldVal));
    return newCommitTime;
  });
}