@Nullable
  public MixedFormatEnumeratorOffset lastEnumeratedOffset() {
    return lastEnumeratedOffset;
  }
State that contains pending mixed-format splits and last enumerator offset in mixed-format source
enumerator {@link MixedFormatSourceEnumerator}.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/enumerator/MixedFormatSourceEnumState.java