### 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)

return bad_type;
		}
		result.kind = GDScriptParser::DataType::BUILTIN;
		result.builtin_type = GDScriptParser::get_builtin_type(first);
		if (result.builtin_type == Variant::ARRAY) {
			GDScriptParser::DataType container_type = type_from_metatype(resolve_datatype(p_type->container_type));
			if (container_type.kind != GDScriptParser::DataType::VARIANT) {
				container_type.is_constant = false;
				result.set_container_element_type(container_type);
			}
		}
	} else if (class_exists(first)) {
		
		result.kind = GDScriptParser::DataType::NATIVE;
		result.builtin_type = Variant::OBJECT;
		result.native_type = first;
	} else if (ScriptServer::is_global_class(first)) {
		if (parser->script_path == ScriptServer::get_global_class_path(first)) {
			result = parser->head->get_datatype();
		} else {
			String path = ScriptServer::get_global_class_path(first);
			String ext = path.get_extension();
			if (ext == GDScriptLanguage::get_singleton()->get_extension()) {
				Ref<GDScriptParserRef> ref = get_parser_for(path);
				if (!ref.is_valid() || ref->raise_status(GDScriptParserRef::INHERITANCE_SOLVED) != OK) {
					push_error(vformat(R"(Could not parse global class "%s" from "%s".)", first, ScriptServer::get_global_class_path(first)), p_type);
					return bad_type;
				}
				result = ref->get_parser()->head->get_datatype();
			} else {