default ContinuousEnumerationResult planSplits(MixedFormatEnumeratorOffset lastPosition) {
    return planSplits(lastPosition, Lists.newArrayList());
  }
Discover the files appended between {@code lastPosition} and current table snapshot
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/enumerator/ContinuousSplitPlanner.java