### 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)
const String lang = (p_language.is_empty()) ? TranslationServer::get_singleton()->get_tool_locale() : p_language;
	// Convert to UTF-16.
	Char16String utf16 = p_string.utf16();
	HashSet<int> breaks;
	UErrorCode err = U_ZERO_ERROR;
	UBreakIterator *bi = ubrk_open(UBRK_LINE, lang.ascii().get_data(), (co_data(), utf16.length(), &err);
	if (U_SUCCESS(err)) {
		while (ubrk_next(bi) != UBRK_DONE) {
			int pos = _convert_pos(p_string, utf16, ubrk_current(bi)) - 1;
			if (pos != p_string.length() - 1) {
				breaks.insert(pos);
			}
		}
		ubrk_close(bi);
	}
	PackedInt32Array ret;
	int line_start = 0;
	int line_end = 0; // End of last word on current line.
	int word_start = 0; // -1 if no word encountered. Leading spaces are part of a word.
	int word_length = 0;
	for (int i = 0; i < p_string.length(); i++) {
		const char32_t c = p_string[i];
		if (is_linebreak(c)) {
			// Force newline.
			ret.push_back(line_start);
			ret.push_back(i);
			line_start = i + 1;
			line_end = line_start;
			word_start = line_start;