editor/naming/node_name_casing not respected by `Add Sun to Scene` and `Add Environment to Scene` buttons

### Tested versions

- Reproducible in: v4.3.dev2.official [352434668]

### System information

Windows 10 & Debian GNU/Linux 11 (bullseye)

### Issue description

The `Add Sun to Scene` and `Add Environment to Scene` buttons for 3D scenes don't respect the `editor/naming/node_name_casing` project setting

### Steps to reproduce

1. change the `editor/naming/node_name_casing` project setting to something other than PascalCase
2. create a new 3D Scene
3. Click the `Add Sun to Scene` and `Add Environment to Scene` buttons in the `Edit Sun and Environment settings` menu
4. see that the `DirectionalLight3D` and `WorldEnvironment` nodes created by those buttons do not follow the case setting

### Minimal reproduction project (MRP)

this can be done with a fresh, empty Godot project. Here's one with `naming/node_name_casing=2` (snake_case)
[casing.zip](https://github.com/godotengine/godot/files/14073752/casing.zip)

Reproduce the issue in a fresh Godot project by changing editor/naming/node_name_casing and using the Add Sun to Scene and Add Environment to Scene buttons in the Edit Sun and Environment settings menu. Trace the handlers for those buttons and verify that the created DirectionalLight3D and WorldEnvironment nodes use the configured casing; done means both names follow the selected setting.

Written by the indexing model from the issue text.