### 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)


switch (err.error) {
					case Callable::CallError::CALL_ERROR_INVALID_ARGUMENT: {
						PropertyInfo wrong_arg = function_info.arguments[err.argument];
						push_error(vformat(R"*(Invalid argument for "%s()" function: argument %d should be "%s" but is "%s".)*", function_name, err.argument + 1,
										   type_from_property(wrong_arg, true).to_string(), p_call->arguments[err.argument]->get_datatype().to_string()),
								p_call->arguments[err.argument]);
					} break;
					case Callable::CallError::CALL_ERROR_INVALID_METHOD:
						push_error(vformat(R"(Invalid call for function "%s".)", function_name), p_call);
						break;
					case Callable::CallError::CALL_ERROR_TOO_MANY_ARGUMENTS:
						push_error(vformat(R"*(Too many arguments for "%s()" call. Expected at most %d but received %d.)*", function_name, err.expected, p_call->arguments.size()), p_call);
						break;
					case Callable::CallError::CALL_ERROR_TOO_FEW_ARGUMENTS:
						push_error(vformat(R"*(Too few arguments for "%s()" call. Expected at least %d but received %d.)*", function_name, err.expected, p_call->arguments.size()), p_call);
						break;
					case Callable::CallError::CALL_ERROR_METHOD_NOT_CONST:
					case Callable::CallError::CALL_ERROR_INSTANCE_IS_NULL:
						break; 
					case Callable::CallError::CALL_OK:
						p_call->is_constant = true;
						p_call->reduced_value = value;
						break;
				}
			} else {
				validate_call_arg(function_info, p_call);
			}
			p_call->set_datatype(type_from_property(function_info.return_val));
			return;
		} else if (Variant::has_utility_function(function_name)) {