### 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)


Ref<GDScript> res = GDScriptCache::get_shallow_script(p_preload->resolved_path, err, parser->script_path);
				p_preload->resource = res;
				if (err != OK) {
					push_error(vformat(R"(Could not preload resource script "%s".)", p_preload->resolved_path), p_preload->path);
				}
			} else if (ResourceLoader::get_resource_type(p_preload->resolved_path) == "PackedScene") {
				Error err = OK;
				Ref<PackedScene> res = GDScriptCache::get_packed_scene(p_preload->resolved_path, err, parser->script_path);
				p_preload->resource = res;
				if (err != OK) {
					push_error(vformat(R"(Could not preload resource scene "%s".)", p_preload->resolved_path), p_preload->path);
				}
			} else {
				p_preload->resource = ResourceLoader::load(p_preload->resolved_path);
				if (p_preload->resource.is_null()) {
					push_error(vformat(R"(Could not preload resource file "%s".)", p_preload->resolved_path), p_preload->path);
				}
			}
		}
	}
	p_preload->is_constant = true;
	p_preload->reduced_value = p_preload->resource;
	p_preload->set_datatype(type_from_variant(p_preload->reduced_value, p_preload));
}
void GDScriptAnalyzer::reduce_self(GDScriptParser::SelfNode *p_self) {
	p_self->is_constant = false;
	p_self->set_datatype(type_from_metatype(parser->current_class->get_datatype()));
	mark_lambda_use_self();
}
void GDScriptAnalyzer::reduce_subscript(GDScriptParser::SubscriptNode *p_subscript, bool p_can_be_pseudo_type) {