protected String name() {
    if (name == null) {
      name = String.format("partition %s of %s", partition, identifier.toString());
    }
    return name;
  }
Segment files has enough content.

<p>1. The total size of all undersized segment files is greater than target size

<p>2. There are two undersized segment file that can be merged into one
amoro-format-iceberg/src/main/java/org/apache/amoro/optimizing/plan/CommonPartitionEvaluator.java