### Godot version

v4.2.dev4.official [549fcce5f]

### System information

Ubuntu 20.04 LTS

### Issue description

See title.

### Steps to reproduce

1. Create a new project
2. Create a csv file that includes the following
```
key,ar
key,placeholder
```
3. Add the generated `.translation` file to Project -> Project Settings... -> Localization
4. In Project -> Project Settings... -> Internationalization -> Locale, set `Test` to `ar`
5. Add a `LineEdit` node and type `-=[]{}`
6. Run the project, and notice that the text is on the right side, but the symbols are incorrectly in LTR (`-=[]{}`).  Correct output is `{}[]=-`
7. Back in the editor, add a single Arabic letter (any will do), and notice that `LineEdit` immediately (and correctly) flips the symbols, and the newly-added Arabic letter, to RTL.

**Notes**
- Identical behavior is seen with `TextEdit`.
- The purpose of steps 2-4 are to simulate an Arabic environment when the project is run, despite `OS.get_locale() == "en"` (or your system's current language).

### Minimal reproduction project

[rtlsymbols.zip](https://github.com/godotengine/godot/files/12525509/rtlsymbols.zip)
if (layout != FONT_LCD_SUBPIXEL_LAYOUT_NONE) {
			mod = (layout << 24);
		}
	}
	if (!_ensure_glyph(fd, size, p_glyph | mod)) {
		return RID(); 
	}
	const HashMap<int32_t, FontGlyph> &gl = fd->cache[size]->glyph_map;
	ERR_FAIL_COND_V(gl[p_glyph | mod].texture_idx < -1 || gl[p_glyph | mod].texture_idx >= fd->cache[size]->textures.size(), RID());
	if (RenderingServer::get_singleton() != nullptr) {
		if (gl[p_glyph | mod].texture_idx != -1) {
			if (fd->cache[size]->textures[gl[p_glyph | mod].texture_idx].dirty) {
				ShelfPackTexture &tex = fd->cache[size]->textures.write[gl[p_glyph | mod].texture_idx];
				Ref<Image> img = Image::create_from_data(tex.texture_w, tex.texture_h, false, tex.format, tex.imgdata);
				if (fd->mipmaps) {
					img->generate_mipmaps();
				}
				if (tex.texture.is_null()) {
					tex.texture = ImageTexture::create_from_image(img);
				} else {
					tex.texture->update(img);
				}
				tex.dirty = false;
			}
			return fd->cache[size]->textures[gl[p_glyph | mod].texture_idx].texture->get_rid();
		}
	}
	return RID();
}
Size2 TextServerAdvanced::_font_get_glyph_texture_size(const RID &p_font_rid, const Vector2i &p_size, int64_t p_glyph) const {