### 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)
// Get NFKD normalizer singleton.
	const UNormalizer2 *unorm = unorm2_getNFKDInstance(&err);
	ERR_FAIL_COND_V_MSG(U_FAILURE(err), TextServer::strip_diacritics(p_string), u_errorName(err));
	// Convert to UTF-16.
	Char16String utf16 = p_string.utf16();
	// Normalize.
	Vector<char16_t> normalized;
	err = U_ZERO_ERROR;
	int32_t len = unorm2_normalize(unorm, utf16.get_data(), -1
	ERR_FAIL_COND_V_MSG(err != U_BUFFER_OVERFLtServer::strip_diacritics(p_string), u_errorName(err));
	normalized.resize(len);
	err = U_ZERO_ERROR;
	unorm2_normalize(unorm, utf16.get_data(), -1, normalized.ptrw(), len, &err);
	ERR_FAIL_COND_V_MSG(U_FAILURE(err), TextServer::strip_diacritics(p_string), u_errorName(err));
	// Convert back to UTF-32.
	String normalized_string = String::utf16(normalized.ptr(), len);
	// Strip combining characters.
	String result;
	for (int i = 0; i < normalized_string.length(); i++) {
		if (u_getCombiningClass(normalized_string[i]
#ifdef GDEXTENSION
			result zed_string[i]);
#else
			result = result + normalized_string[i];
#endif
		}
	}
	return result;
}
String TextServerAdvanced::_string_to_upper(const String &p_string, const String &p_language) const {