[Bug] Grafana Plugin - variables not accepted in SQL "Drop Down List" query editor

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Version

IoTDB v1.3.2 in docker on MacOS

### Describe the bug and provide the minimal reproduce step

A variable for a device path has been created as per instructions.
This variable can be used successfully in the "SQL Full-Customized" query editor

As per the excellent documentation [1]

> Both SQL: Full Customized and *SQL: Drop-down List* input methods support the variable and template functions of grafana

However, trying to add the sensor path at the dropdown element shown as `"$endpoint"` below ...

[root] > [dropdown-sg] > "$endpoint"

... I get the following error:

> $endpoint is illegal, unquoted node name can only consist of digits, characters and underscore, or start or end with wildcard

Note: I have tried `$endpoint` `${endpoint}` and `{{endpoint}}` form of variable template syntax.

[1]: https://iotdb.apache.org/UserGuide/latest/Ecosystem-Integration/Grafana-Plugin.html#create-a-new-panel

### What did you expect to see?

Variable template syntax shown in path element instead of regular path component from dropdown

### What did you see instead?

Error

### Anything else?

I notice the source repo for the grafana plugin (iotdb-extras) does not have any issues tracked. I can re-submit there if required.

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Commencez par reproduire le problème dans l’éditeur SQL Drop-down List du plugin Grafana avec IoTDB v1.3.2, en le comparant à l’éditeur SQL Full-Customized. Examinez ensuite le code source du plugin dans iotdb-extras ainsi que la documentation liée du plugin Grafana. Le travail est considéré comme terminé lorsqu’une variable de chemin de périphérique est acceptée dans l’éditeur déroulant au lieu d’être analysée comme un nœud de chemin littéral illégal.

Rédigé par le modèle d'indexation à partir du texte de l'issue.