[Java][Docs] Document the use of the batchSize argument in Dataset ScanOptions

Several ScanOptions methods take a batchSize argument as shown: 

`public ScanOptions(long batchSize) {`
`    this(batchSize, Optional.empty());`
``}

Since the scanner reads one ArrowRecordBatch per load invocation, setting the parameter to a size larger than the RecordBatch has no effect. It only works when it's smaller than the number of rows in the RecordBatch, (i.e., the number or records read is equal to min(batchSize, recordBatch rowCount), potentially leading to some confusion. 

**Reporter**: [Larry White](https://issues.apache.org/jira/browse/ARROW-17346) / @lwhite1

_{**Note**: *This issue was originally created as [ARROW-17346](https://issues.apache.org/jira/browse/ARROW-17346). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

從接受 batchSize 的 Dataset ScanOptions 方法開始，追蹤掃描器如何在每次呼叫時載入一個 ArrowRecordBatch。記錄大於 RecordBatch 列數的值不會產生額外效果，而較小的值會將記錄數限制為 min(batchSize, recordBatch rowCount)；當 ScanOptions 文件清楚說明此行為時，即表示完成。

由索引模型根據 Issue 內容生成。