### 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)


src_native = GDScriptNativeClass::get_class_static();
			} else {
				src_native = p_source.native_type;
			}
			break;
		case GDScriptParser::DataType::SCRIPT:
			if (p_target.kind == GDScriptParser::DataType::CLASS) {
				
				return false;
			}
			if (p_source.is_meta_type) {
				src_native = p_source.script_type->get_class_name();
			} else {
				src_script = p_source.script_type;
				src_native = src_script->get_instance_base_type();
			}
			break;
		case GDScriptParser::DataType::CLASS:
			if (p_source.is_meta_type) {
				src_native = GDScript::get_class_static();
			} else {
				src_class = p_source.class_type;
				const GDScriptParser::ClassNode *base = src_class;
				while (base->base_type.kind == GDScriptParser::DataType::CLASS) {
					base = base->base_type.class_type;
				}
				src_native = base->base_type.native_type;
				src_script = base->base_type.script_type;
			}
			break;