### 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)


GDScriptParser::DataType parent_return_type;
		List<GDScriptParser::DataType> parameters_types;
		int default_par_count = 0;
		BitField<MethodFlags> method_flags;
		StringName native_base;
		if (!p_is_lambda && get_function_signature(p_function, false, base_type, function_name, parent_return_type, parameters_types, default_par_count, method_flags, &native_base)) {
			bool valid = p_function->is_static == method_flags.has_flag(METHOD_FLAG_STATIC);
			valid = valid && parent_return_type == p_function->get_datatype();
			int par_count_diff = p_function->parameters.size() - parameters_types.size();
			valid = valid && par_count_diff >= 0;
			valid = valid && default_value_count >= default_par_count + par_count_diff;
			int i = 0;
			for (const GDScriptParser::DataType &par_type : parameters_types) {
				valid = valid && par_type == p_function->parameters[i++]->get_datatype();
			}
			if (!valid) {
				
				String parent_signature = String(function_name) + "(";
				int j = 0;
				for (const GDScriptParser::DataType &par_type : parameters_types) {
					if (j > 0) {
						parent_signature += ", ";
					}
					String parameter = par_type.to_string();
					if (parameter == "null") {
						parameter = "Variant";
					}
					parent_signature += parameter;
					if (j >= parameters_types.size() - default_par_count) {
						parent_signature += " = <default>";