[GDExtension ]A class which inherit from `EditorPlugin` can't be recognized correctly in editor.

First, code a class `TestEditorPlugin` which inherit from `EditorPlugin` in cpp:
```
class TestEditorPlugin: public EditorPlugin{
GDCLASS(TestEditorPlugin, EditorPlugin)
protected:
static void _bind_methods(){}
};
```

Second, code a simple editor plugin which extends form `TestEditorPlugin`:
[plugin.gd]
```
@tool
extends TestEditorPlugin
```

Last, enable it in editor, will popup an error:

As you can see, the `TestEditorPlugin` is recognized in editor and the help document show that it is inherit from `EditorPlgin`.

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My target is to develop a plugin in cpp without using GDScripts or any scenes ( I think GDExtension should provide some callback after editor boot finished, we can add our cpp plugin manually), But it seems there is no way to achive, so I try to using a simple plugin to setup my cpp plugin, and the result is weird.