### 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)
bnert("mni")); // Manipuri
		bnert("mni_IN"));
		bnert("mni_Beng"));
		bnert("mni_Beng_IN"));
		bn.digits = U"০১২৩৪৫৬৭৮৯.";
		bnsign = U"%";
		bn.exp = U"e";
		num_systems.push_back(bn);
	}
	// Devanagari numerals.
	{
		NumSystemData mr;
		ame("mr")); // Marathi
		ame("mr_IN"));
		ame("ne")); // Nepali
		ame("ne_IN"));
		ame("ne_NP"));
		ame("sa")); // Sanskrit
		ame("sa_IN"));
		mr.digits = U"०१२३४५६७८९.";
		mrsign = U"%";
		mr.exp = U"e";
		num_systems.push_back(mr);
	}
	// Dzongkha numerals.
	{
		NumSystemData dz;
		dzert(Stringkha
		dzert("dz_BT"));
		dz.digits = U"༠;