### 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)


if (!class_exists(base_native)) {
			push_error(vformat("Native class %s used in script doesn't exist or isn't exposed.", base_native), p_source);
			return false;
		} else if (p_is_constructor && !ClassDB::can_instantiate(base_native)) {
			if (p_base_type.kind == GDScriptParser::DataType::CLASS) {
				push_error(vformat(R"(Class "%s" cannot be constructed as it is based on abstract native class "%s".)", p_base_type.class_type->fqcn.get_file(), base_native), p_source);
			} else if (p_base_type.kind == GDScriptParser::DataType::SCRIPT) {
				push_error(vformat(R"(Script "%s" cannot be constructed as it is based on abstract native class "%s".)", p_base_type.script_path.get_file(), base_native), p_source);
			} else {
				push_error(vformat(R"(Native class "%s" cannot be constructed as it is abstract.)", base_native), p_source);
			}
			return false;
		}
	}
	if (p_is_constructor) {
		function_name = GDScriptLanguage::get_singleton()->strings._init;
		r_method_flags.set_flag(METHOD_FLAG_STATIC);
	}
	GDScriptParser::ClassNode *base_class = p_base_type.class_type;
	GDScriptParser::FunctionNode *found_function = nullptr;
	while (found_function == nullptr && base_class != nullptr) {
		if (base_class->has_member(function_name)) {
			if (base_class->get_member(function_name).type != GDScriptParser::ClassNode::Member::FUNCTION) {
				
				push_error(vformat(R"(Member "%s" is not a function.)", function_name), p_source);
				return false;
			}
			resolve_class_member(base_class, function_name, p_source);