### Godot version

4.1.beta3

### System information

Fedora Workstation 38 - Godot 4.1.beta3 - Vulkan (Forward+)

### Issue description

**This is an issue created by the production team, we're working on it**

Currently, it's impossible to call virtual functions within GDScript.

This currently returns an error:
```gdscript
# a.gd
extends Node

func _process(delta: float) -> void:
	pass
```

```gdscript
# main.gd
extends Node

var my_node: Node = preload("res://a.gd").new()

func _process(delta: float) -> void:
	my_node._process(delta)  # Cannot call virtual function "_process()" because it hasn't been defined.
```

### Steps to reproduce

1. Create a script (`a.gd`) based on `Node` that declares `_process()`;
2. Create a main node;
3. Attach a script to the main node;
4. Initialize a variable with a new `a.gd` instance;
5. Try to run `_process()` on that node;
6. Find out that it returns an error.

### Minimal reproduction project

[virtual_functions.zip (updated)](https://github.com/godotengine/godot/files/11823992/virtual_functions.zip)


GDScriptParser::DataType class_type;
	class_type.is_constant = true;
	class_type.is_meta_type = true;
	class_type.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	class_type.kind = GDScriptParser::DataType::CLASS;
	class_type.class_type = p_class;
	class_type.script_path = parser->script_path;
	class_type.builtin_type = Variant::OBJECT;
	p_class->set_datatype(class_type);
	GDScriptParser::DataType result;
	if (!p_class->extends_used) {
		result.type_source = GDScriptParser::DataType::ANNOTATED_INFERRED;
		result.kind = GDScriptParser::DataType::NATIVE;
		result.native_type = SNAME("RefCounted");
	} else {
		result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
		GDScriptParser::DataType base;
		int extends_index = 0;
		if (!p_class->extends_path.is_empty()) {
			if (p_class->extends_path.is_relative_path()) {
				p_class->extends_path = class_type.script_path.get_base_dir().path_join(p_class->extends_path).simplify_path();
			}
			Ref<GDScriptParserRef> ext_parser = get_parser_for(p_class->extends_path);
			if (ext_parser.is_null()) {
				push_error(vformat(R"(Could not resolve super class path "%s".)", p_class->extends_path), p_class);
				return ERR_PARSE_ERROR;
			}
			Error err = ext_parser->raise_status(GDScriptParserRef::INHERITANCE_SOLVED);
			if (err != OK) {
				push_error(vformat(R"(Could not resolve super class inheritance from "%s".)", p_class->extends_path), p_class);