### 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)
gl.index = glyph_info[i].codepoint;
			if (gl.index != 0) {
				_ensure_glyph(fd, fss, gl.index | mod);
				if (p_sd->orientation == ORIENTATION_HORIZONTAL) {
					if (subpos) {
						gl.advance = (double)glyph_pos[i].x_advance / (64.0 / scale) + ea;
					} else {
						gl.advance = Math::round((double)glyph_pos[i].x_advance / (64.0 / scale) + ea);
					}
				} else {
					gl.advance = -Math::round((double)glyph_pos[i].y_advance / (64.0 / scale));
				}
				if (subpos) {
					gl.x_off = (double)glyph_pos[i].x_offset / (64.0 / scale);
				} else {
					gl.x_off = Math::round((double)glyph_pos[i].x_offset / (64.0 / scale));
				}
				gl.y_off = -Math::round((double)glyph_pos[i].y_offset / (64.0 / scale));
			}
			if (!last_run || i < glyph_count - 1) {
				
				if (sp_sp && is_whitespace(p_sd->text[glyph_info[i].cluster])) {
					gl.advance += sp_sp;
				} else {
					gl.advance += sp_gl;
				}
			}
			if (p_sd->preserve_control) {
				last_cluster_valid = last_cluster_valid && ((glyph_info[i].codepoint != 0) || (p_sd->text[glyph_info[i].cluster] == 0x0009) || (u_isblank(p_sd->text[glyph_info[i].cluster]) && (gl.advance != 0)) || (!u_isblank(p_sd->text[glyph_info[i].cluster]) && is_linebreak(p_sd->text[glyph_info[i].cluster])));
			} else {