### 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)


for (int i = 0; i < p_array->elements.size(); i++) {
		GDScriptParser::ExpressionNode *element = p_array->elements[i];
		reduce_expression(element);
	}
	
	GDScriptParser::DataType arr_type;
	arr_type.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	arr_type.kind = GDScriptParser::DataType::BUILTIN;
	arr_type.builtin_type = Variant::ARRAY;
	arr_type.is_constant = true;
	p_array->set_datatype(arr_type);
}
#ifdef DEBUG_ENABLED
static bool enum_has_value(const GDScriptParser::DataType p_type, int64_t p_value) {