### Godot version

4.1.1

### System information

windows 11

### Issue description

When registering a type with class_name and using that class name to declare a variable in code only, autocomplete works as expected anywhere in other nodes/scenes. However, if making a custom scene node that extends a script with the class_name, if that custom scene is instantiated in a different scene, even if the type is specified, it only shows the parent node's functions and not any of the extended functionality. I have made a basic project showing the issue

### Steps to reproduce

I have made a very simple project showing the issue. https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue essentially, the extended Node scene will only show the custom function when both the type is specified as well as the type afterwards following "as" 
e.g. `@onready var my_class_4: MyClass = $MyClass4 as MyClass`

### Minimal reproduction project

https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue
ClassDB::get_integer_constant(context.current_class->extends[0]->name, p_symbol, &success);
		if (success) {
			r_result.type = ScriptLanguage::LOOKUP_RESULT_CLASS_CONSTANT;
			r_result.class_name = context.current_class->extends[0]->name;
			r_result.class_member = p_symbol;
			return OK;
		}
	}
	bool is_function = false;
	switch (context.type) {
		case GDScriptParser::COMPLETION_BUILT_IN_TYPE_CONSTANT_OR_STATIC_METHOD: {
			if (!Variant::has_builtin_method(context.builtin_type, StringName(p_symbol))) {
				
				r_result.type = ScriptLanguage::LOOKUP_RESULT_CLASS_CONSTANT;
				r_result.class_name = Variant::get_type_name(context.builtin_type);
				r_result.class_member = p_symbol;
				return OK;
			}
			
			GDScriptParser::DataType base_type;
			base_type.kind = GDScriptParser::DataType::BUILTIN;
			base_type.builtin_type = context.builtin_type;
			if (_lookup_symbol_from_base(base_type, p_symbol, true, r_result) == OK) {
				return OK;
			}
		} break;
		case GDScriptParser::COMPLETION_SUPER_METHOD:
		case GDScriptParser::COMPLETION_METHOD: {
			is_function = true;
			[[fallthrough]];