### 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)
}
	FontAdvanced *fd = font_owner.get_or_null(f);
	ERR_FAIL_COND(!fd);
	MutexLock lock(fd->mutex);
	Vector2i fss = _get_size(fd, fs);
	hb_font_t *hb_font = _font_get_hb_handle(f, fs);
	double scale = _font_get_scale(f, fs);
	double sp_sp = p_sd->extra_spacing[SPACING_SPACE] + _font_get_spacing(f, SPACING_SPACE);
	double sp_gl = p_sd->extra_spacing[SPACING_GLYPH] + _font_get_spacing(f, SPACING_GLYPH);
	bool last_run = (p_sd->end == p_end);
	double ea = _get_extra_advance(f, fs);
	bool subpos = (scale != 1.0) || (_font_get_subpixel_positioning(f) == SUBPIXEL_POSITIONING_ONE_HALF) || (_font_get_subpixel_positioning(f) == SUBPIXEL_POSITIONING_ONE_QUARTER) || (_font_get_subpixel_positioning(f) == SUBPIXEL_POSITIONING_AUTO && fs <= SUBPIXEL_POSITIONING_ONE_HALF_MAX_SIZE);
	ERR_FAIL_COND(hb_font == nullptr);
	hb_buffer_clear_contents(p_sd->hb_buffer);
	hb_buffer_set_direction(p_sd->hb_buffer, p_direction);
	int flags = (p_start == 0 ? HB_BUFFER_FLAG_BOT : 0) | (p_end == p_sd->text.length() ? HB_BUFFER_FLAG_EOT : 0);
	if (p_sd->preserve_control) {
		flags |= HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES;
	} else {
		flags |= HB_BUFFER_FLAG_DEFAULT;
	}
#if HB_VERSION_ATLEAST(5, 1, 0)
	flags |= HB_BUFFER_FLAG_PRODUCE_SAFE_TO_INSERT_TATWEEL;
#endif
	hb_buffer_set_flags(p_sd->hb_buffer, (hb_buffer_flags_t)flags);
	hb_buffer_set_script(p_sd->hb_buffer, p_script);
	if (p_sd->spans[p_span].language.is_empty()) {
		hb_language_t lang = hb_language_from_string(TranslationServer::get_singleton()->get_tool_locale().ascii().get_data(), -1);
		hb_buffer_set_language(p_sd->hb_buffer, lang);
	} else {