### 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 bad_type;
	bad_type.kind = GDScriptParser::DataType::VARIANT;
	bad_type.type_source = GDScriptParser::DataType::INFERRED;
	if (p_type == nullptr) {
		return bad_type;
	}
	if (p_type->get_datatype().is_resolving()) {
		push_error(R"(Could not resolve datatype: Cyclic reference.)", p_type);
		return bad_type;
	}
	if (!p_type->get_datatype().has_no_type()) {
		return p_type->get_datatype();
	}
	GDScriptParser::DataType resolving_datatype;
	resolving_datatype.kind = GDScriptParser::DataType::RESOLVING;
	p_type->set_datatype(resolving_datatype);
	GDScriptParser::DataType result;
	result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	if (p_type->type_chain.is_empty()) {
		
		result.kind = GDScriptParser::DataType::BUILTIN;
		result.builtin_type = Variant::NIL;