### Godot version

v4.0.rc1.official [8843d9ad3]

### System information

Lubuntu

### Issue description

You can't use + or += to mutate typed arrays.

It seems to be not correctly getting the type information from the second operand.

An erudite poster on the discord puts it differently:
> it's more like operator + doesn't retain Array typing
> the syntax for Array Concatenation via operators, but the idea gets across i think


The error you see is:
```Trying to assign an array of type "Array" to a variable of type "Array[int]".```


### Steps to reproduce

```
	var Alice: Array[int] = [1,2,3]
	var Bob: Array[int] = [4,5,6]
	Alice += Bob
```
This will crash with the above error message.

### Minimal reproduction project

[plus_syntax_broken_demo_project.zip](https://github.com/godotengine/godot/files/10694514/plus_syntax_broken_demo_project.zip)

StringName native_base = p_native_class;
	while (true && native_base != StringName()) {
		if (ClassDB::has_enum(native_base, p_enum_name, true)) {
			break;
		}
		native_base = ClassDB::get_parent_class_nocheck(native_base);
	}
	GDScriptParser::DataType type = make_enum_type(p_enum_name, native_base, p_meta);
	if (p_meta) {
		type.builtin_type = Variant::NIL; 
	}
	List<StringName> enum_values;
	ClassDB::get_enum_constants(native_base, p_enum_name, &enum_values, true);
	for (const StringName &E : enum_values) {
		type.enum_values[E] = ClassDB::get_integer_constant(native_base, E);
	}
	return type;
}
static GDScriptParser::DataType make_global_enum_type(const StringName &p_enum_name, const StringName &p_base, bool p_meta = true) {