What purpose does ArrowRecordBatch solve?

I was going through the [Flight Java Example](https://arrow.apache.org/cookbook/java/flight.html) and was wondering if we can persist `VectorSchemaRoot` directly in the `Dataset` instead of `ArrowRecordBatch` list?

```java
class Dataset implements AutoCloseable {
private final List batches;
private final Schema schema;
private final long rows;
public Dataset(List batches, Schema schema, long rows) {
this.batches = batches;
this.schema = schema;
this.rows = rows;
}
public List getBatches() {
return batches;
}
public Schema getSchema() {
return schema;
}
public long getRows() {
return rows;
}
@Override
public void close() throws Exception {
AutoCloseables.close(batches);
}
}
```

Start with the linked Flight Java Example and the Dataset snippet in the issue. Compare the roles and lifecycle of VectorSchemaRoot and ArrowRecordBatch, then determine whether the example or its documentation should explain the distinction. Done means the intended representation and ownership behavior are clearly documented.

Written by the indexing model from the issue text.