rescale() {
    if (!this.isValid) return this;
    const vals = removeZeroes(this.normalize().shiftToAll().toObject());
    return clone(this, { values: vals }, true);
  }
Rescale units to its largest representation
@example Duration.fromObject({ milliseconds: 90000 }).rescale().toObject() //=> { minutes: 1, seconds: 30 }
@return {Duration}