The Create New Node dialog does not show plugin custom controls when plugin is disabled

### Tested versions

- Reproducible in v4.3.stable.official [77dcf97d8]

### System information

Godot v4.3.stable - Windows 10.0.26100 - Vulkan (Forward+) - integrated Intel(R) UHD Graphics 630 (Intel Corporation; 30.0.101.1404) - Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz (16 Threads)

### Issue description

The Create New Node dialog does not include custom controls if the control script is within the editor plugin folder and the plugin is disabled. This creates a major problem since editing a plugin scene with the plugin enabled can have negative side effects and potentially crash the editor. Additionally, once a custom plugin control is added to a scene it remains in the scene tree even when the plugin is disabled.

### Steps to reproduce

1. Create an editor plugin addon. Do not enable the plugin
2. Create a custom control script in the plugin folder (e.g. extends Button)
3. Open a scene for editing
4. Right click scene node
5. Click Add Child Node
6. Search for the custom control, it will not be listed
7. Enable the plugin
8. Repeat steps 5 through 7, the custom control will be listed
9. Add the custom control to the scene tree
10. Disable the plugin, the custom control is still in the scene tree

### Minimal reproduction project (MRP)

[plugin_control_bug.zip](https://github.com/user-attachments/files/18657688/plugin_control_bug.zip)