### 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
theme->set_icon("radio_checked", "PopupMenu", theme->get_icon(SNAME("GuiRadioChecked"), SNAME("EditorIcons")));
	theme->set_icon("radio_unchecked", "PopupMenu", theme->get_icon(SNAME("GuiRadioUnchecked"), SNAME("EditorIcons")));
	theme->set_icon("checked_disabled", "PopupMenu", theme->get_icon(SNAME("GuiCheckedDisabled"), SNAME("EditorIcons")));
	theme->set_icon("unchecked_disabled", "PopupMenu", theme->get_icon(SNAME("GuiUncheckedDisabled"), SNAME("EditorIcons")));
	theme->set_icon("radio_checked_disabled", "PopupMenu", theme->get_icon(SNAME("GuiRadioCheckedDisabled"), SNAME("EditorIcons")));
	theme->set_icon("radio_unchecked_disabled", "PopupMenu", theme->get_icon(SNAME("GuiRadioUncheckedDisabled"), SNAME("EditorIcons")));
	theme->set_icon("submenu", "PopupMenu", theme->get_icon(SNAME("ArrowRight"), SNAME("EditorIcons")));
	theme->set_icon("submenu_mirrored", "PopupMenu", theme->get_icon(SNAME("ArrowLeft"), SNAME("EditorIcons")));
	theme->set_icon("visibility_hidden", "PopupMenu", theme->get_icon(SNAME("GuiVisibilityHidden"), SNAME("EditorIcons")));
	theme->set_icon("visibility_visible", "PopupMenu", theme->get_icon(SNAME("GuiVisibilityVisible"), SNAME("EditorIcons")));
	theme->set_icon("visibility_xray", "PopupMenu", theme->get_icon(SNAME("GuiVisibilityXray"), SNAME("EditorIcons")));
	
	
	
	const int vsep_base = extra_spacing + default_margin_size + 6;
	const int force_even_vsep = vsep_base + (vsep_base % 2);
	theme->set_constant("v_separation", "PopupMenu", force_even_vsep * EDSCALE);
	theme->set_constant("outline_size", "PopupMenu", 0);
	theme->set_constant("item_start_padding", "PopupMenu", default_margin_size * 1.5 * EDSCALE);
	theme->set_constant("item_end_padding", "PopupMenu", default_margin_size * 1.5 * EDSCALE);
	
	for (int i = 0; i < 16; i++) {
		Color si_base_color = accent_color;
		float hue_rotate = (i * 2 % 16) / 16.0;
		si_base_color.set_hsv(Math::fmod(float(si_base_color.get_h() + hue_rotate), float(1.0)), si_base_color.get_s(), si_base_color.get_v());
		si_base_color = accent_color.lerp(si_base_color, float(EDITOR_GET("docks/property_editor/subresource_hue_tint")));
		
		Ref<StyleBoxFlat> sub_inspector_bg = style_default->duplicate();
		sub_inspector_bg->set_bg_color(dark_color_1.lerp(si_base_color, 0.08));
		sub_inspector_bg->set_border_width_all(2 * EDSCALE);