`get_windows()` returns all root items

Windows 10
Python v3.14.3
DearPyGui v2.2.0

```python
import dearpygui.dearpygui as dpg

dpg.create_context()
dpg.setup_dearpygui()

dpg.add_window()
dpg.add_theme()
dpg.add_handler_registry()
dpg.add_item_handler_registry()

assert len(dpg.get_windows()) != 4, "too many items"
```

The issue with fixing this is that it's nice to have a performant option to get all top-level items. It's also behaved like this for...awhile, so maybe it's best to not fix it (although documenting it might be helpful).

Maybe we could make a new function, instead? Something like:
```python
def get_existing_items(item_types: Sequence[int] | None = None) -> list[int]: ...
```
...where all items are returned when `item_types == None` (the current behavior of `get_windows()`) . Otherwise, only return items of types contained in `item_types`. Whether we fix it or create a new function, I can work on a PR for it.