`CanvasGroup` does not include the full extents of any control nodes drawing outside their rect

### Tested versions

Reproducible in:
- v4.6.dev [bd2ca13c6] (master)
- v4.5.stable.official [876b29033]

### System information

Godot v4.6.dev (bd2ca13c6) - Nobara Linux 42 (KDE Plasma Desktop Edition) on Wayland - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3070 (nvidia; 580.105.08) - AMD Ryzen 9 5900X 12-Core Processor (24 threads) - 31.25 GiB memory

### Issue description

When putting a Control node that draws outside its bounds - be it through `_draw()` or otherwise, such as a panel's stylebox utilizing skew or expand margins - under a CanvasGroup node, not all of the control node's drawn visuals will be included.

This can be seen by increasing the CanvasGroup's fit margin.

https://github.com/user-attachments/assets/1d0f77a7-5492-4736-a5ca-e2205bbb20e1

### Steps to reproduce

1. Download and open the MRP.
2. Increase the fit margin of the CanvasGroup root node in the scene.
3. Observe that more of the control's custom `draw_rect()` call is now visible.

### Minimal reproduction project (MRP)

[canvas-group-control-draw.zip](https://github.com/user-attachments/files/23546442/canvas-group-control-draw.zip)

Start with the attached minimal reproduction project, focusing on the CanvasGroup root, its fit margin, and the Control node's custom draw_rect() output. Reproduce the clipping with the fit margin unchanged, then verify that the full visuals drawn outside the Control rect are included without requiring an increased fit margin.

Written by the indexing model from the issue text.