Symbol lookup does not recognize internal classes inherited from other internal classes

### Tested versions

4.7 dev3

### System information

W10

### Issue description

The title might be confusing, but it boils down to:
```GDScript
class Class1:
pass

class Class2 extends Class1:
var p: Class1
```
When you try to Ctrl+Click Class1 referenced after extends or the `p` variable, it won't be recognized. Here, I'm holding Ctrl all the time:

https://github.com/user-attachments/assets/d3f14caf-938c-4f04-aa6a-0d4b8f5ddd3c

See how Class1 reference is not underlined.

### Steps to reproduce

Use the code above.

### Minimal reproduction project (MRP)

N/A

Start by reproducing the issue in the GDScript example from the report and trace the editor's Ctrl+Click symbol lookup for the `extends` reference and the typed variable. Done means internal classes inherited from other internal classes are recognized and navigable in both locations.

Written by the indexing model from the issue text.