### 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)


is_self = true;
		if (p_call->callee == nullptr && !lambda_stack.is_empty()) {
			push_error("Cannot use `super()` inside a lambda.", p_call);
		}
	} else if (callee_type == GDScriptParser::Node::IDENTIFIER) {
		base_type = parser->current_class->get_datatype();
		base_type.is_meta_type = false;
		is_self = true;
	} else if (callee_type == GDScriptParser::Node::SUBSCRIPT) {
		GDScriptParser::SubscriptNode *subscript = static_cast<GDScriptParser::SubscriptNode *>(p_call->callee);
		if (subscript->base == nullptr) {
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		if (!subscript->is_attribute) {
			
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		if (subscript->attribute == nullptr) {
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		GDScriptParser::IdentifierNode *base_id = nullptr;