GDExtension classes inheriting from Resource are not using icons in FileSystem

[Withaust]

Tested versions

4.3 dev 1

System information

Windows 10 Godot 4.3 dev 1 Vulkan

Issue description

I am aware there is #32706, but it does not seem to cover GDExtensions.

Currently, GDExtension classes inheriting from Resource are not using icons in FileSystem. It seems to work in every other place, but not in FileSystem for some reason.

Steps to reproduce

1. Create a class in GDExtension that inherits Resource
2. Assign an icon in .gdextension file to said class
3. Observe how FileSystem is using default icon for this class, while the property viewer is displaying everything as expected

Minimal reproduction project (MRP)

You can see an example in the root of the project here

IconTest.zip

[akien-mga]

Confirmed in 4.3.stable.

[SaNeOr]

I've tested it, and found the same problem when using gdscript to inherit from resourcesubclasses, but there is another special feature of gdextension's icon, should need to get_class_icon() to get the icon_path.