### Godot version

v4.1.1.stable.official [bd6af8e0e]

### System information

Godot v4.1.1.stable - Ubuntu 22.04.2 LTS 22.04 - Vulkan (Forward+) - integrated Intel(R) UHD Graphics 615 (AML-KBL) () - Intel(R) Core(TM) i3-10100Y CPU @ 1.30GHz (4 Threads)

### Issue description

Summary: When editing the subregion of a StyleBoxTexture, it shows me the entire spritesheet of the Atlas texture, instead of the selected portion of the atlas, making it difficult (and non-intuitive) to correctly select the subregion I need. 

What I expect: I understand that the sub-region may be used to emulate the behavior of a nine-patch. So I would expect to see there the subregion that i selected previously from the Atlas as the texture to be shown.

I have only tested this in a Panel Container

### Steps to reproduce

I found this problem when doing these steps:

- Add a PanelContainer node
- In the inspector select Theme Overrrides -> Style -> new StyleBoxTexture
- In the texture of the StyleBoxTexture select new AtlasTexture
- Dropped the spritesheet in the Atlas of the AtlasTexture
- In Region of the AtlasTexture, selected Edit Region and drew the rectangle on the texture i want:
![image](https://github.com/godotengine/godot/assets/1207326/2e9624b1-63bc-4267-8d7f-59e82df7896e)

- Back in the StyleBoxTexture options, in Sub-Region, clicked on Edit Region to select the nine-patch region i need
- Here is where the region editor shows me the entire spritesheet and not the sub-texture i selected from the atlas. The image below shows the axis correctly positioned for the nine-patch to work, but it is not intuitive because it has to be positioned without seeing the correct texture, making it difficult to finetune for some textures.

![image](https://github.com/godotengine/godot/assets/1207326/a5023afd-7e4b-47c8-adfc-03fda7f6301b)


### Minimal reproduction project

N/A
sub_inspector_bg->set_border_color(si_base_color * Color(0.7, 0.7, 0.7, 0.8));
		sub_inspector_bg->set_content_margin_all(4 * EDSCALE);
		sub_inspector_bg->set_corner_radius(CORNER_TOP_LEFT, 0);
		sub_inspector_bg->set_corner_radius(CORNER_TOP_RIGHT, 0);
		theme->set_stylebox("sub_inspector_bg" + itos(i), "Editor", sub_inspector_bg);
		
		Ref<StyleBoxFlat> bg_color = make_flat_stylebox(si_base_color * Color(0.7, 0.7, 0.7, 0.8), 0, 0, 0, 0, corner_radius);
		bg_color->set_anti_aliased(false);
		bg_color->set_corner_radius(CORNER_BOTTOM_LEFT, 0);
		bg_color->set_corner_radius(CORNER_BOTTOM_RIGHT, 0);
		theme->set_stylebox("sub_inspector_property_bg" + itos(i), "Editor", bg_color);
	}
	theme->set_color("sub_inspector_property_color", "Editor", dark_theme ? Color(1, 1, 1, 1) : Color(0, 0, 0, 1));
	
	theme->set_color("label_color", "EditorSpinSlider", font_color);
	theme->set_color("read_only_label_color", "EditorSpinSlider", font_readonly_color);
	Ref<StyleBoxFlat> editor_spin_label_bg = style_default->duplicate();
	editor_spin_label_bg->set_bg_color(dark_color_3);
	editor_spin_label_bg->set_border_width_all(0);
	theme->set_stylebox("label_bg", "EditorSpinSlider", editor_spin_label_bg);
	
	Ref<StyleBoxFlat> style_property_bg = style_default->duplicate();
	style_property_bg->set_bg_color(highlight_color);
	style_property_bg->set_border_width_all(0);
	Ref<StyleBoxFlat> style_property_child_bg = style_default->duplicate();
	style_property_child_bg->set_bg_color(dark_color_2);
	style_property_child_bg->set_border_width_all(0);
	theme->set_constant("font_offset", "EditorProperty", 8 * EDSCALE);
	theme->set_stylebox("bg_selected", "EditorProperty", style_property_bg);
	theme->set_stylebox("bg", "EditorProperty", Ref<StyleBoxEmpty>(memnew(StyleBoxEmpty)));