Refactor `backup/IoTDBDataBackTool.java` to resolve SonarQube issues

## Description

This task focuses on resolving multiple SonarCloud issues identified in `backup/IoTDBDataBackTool.java`.The file currently contains several maintainability and code quality violations, including:

- Update this logger to use "IoTDBDataBackTool.class".
- Rename this field "IS_OBJECT_STORAGE" to match the regular expression '^[a-z][a-zA-Z0-9]*$'.
- Use "isEmpty()" to check whether a "String" is empty or not.

## File
`iotdb-client/.../org/apache/iotdb/tool/backup/IoTDBDataBackTool.java`

## How to fix

```tsx
1.
LoggerFactory.getLogger(AbstractDataTool.class);
to
LoggerFactory.getLogger(IoTDBDataBackTool.class);

2.

static boolean IS_OBJECT_STORAGE = false;
to
static boolean isObjectStorage = false;

3.
targetWalDirParam.length() > 0;
to
targetWalDirParam.isEmpty();
```

## Sonar Issue

https://sonarcloud.io/project/issues?open=AY8JzfmBywzNF5Ghx44F&id=apache_iotdb

`Note: The goal is to improve readability, maintainability, and compliance with SonarCloud quality standards without changing existing functionality.`

Comienza con iotdb-client/.../org/apache/iotdb/tool/backup/IoTDBDataBackTool.java y revisa los hallazgos de SonarCloud indicados en el issue. Actualiza de forma coherente en todo el archivo la clase logger, la nomenclatura de los campos y la comprobación de cadena vacía; después, verifica que la herramienta de backup siga compilándose y comportándose sin cambios funcionales.

Escrito por el modelo de indexación a partir del texto del issue.