### 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)


found_function = base_class->get_member(function_name).function;
		}
		resolve_class_inheritance(base_class, p_source);
		base_class = base_class->base_type.class_type;
	}
	if (found_function != nullptr) {
		if (p_is_constructor || found_function->is_static) {
			r_method_flags.set_flag(METHOD_FLAG_STATIC);
		}
		for (int i = 0; i < found_function->parameters.size(); i++) {
			r_par_types.push_back(found_function->parameters[i]->get_datatype());
			if (found_function->parameters[i]->initializer != nullptr) {
				r_default_arg_count++;
			}
		}
		r_return_type = p_is_constructor ? p_base_type : found_function->get_datatype();
		r_return_type.is_meta_type = false;
		r_return_type.is_coroutine = found_function->is_coroutine;
		return true;
	}
	Ref<Script> base_script = p_base_type.script_type;
	while (base_script.is_valid() && base_script->has_method(function_name)) {
		MethodInfo info = base_script->get_method_info(function_name);
		if (!(info == MethodInfo())) {
			return function_signature_from_info(info, r_return_type, r_par_types, r_default_arg_count, r_method_flags);
		}
		base_script = base_script->get_base_script();
	}
	
	if (p_base_type.is_meta_type && !p_is_constructor && (p_base_type.kind == GDScriptParser::DataType::SCRIPT || p_base_type.kind == GDScriptParser::DataType::CLASS)) {