### 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)


return; 
			}
			
			
			if (p_identifier->source == GDScriptParser::IdentifierNode::UNDEFINED_SOURCE || p_identifier->source == GDScriptParser::IdentifierNode::MEMBER_CONSTANT) {
				return;
			}
			GDScriptParser::FunctionNode *function_test = lambda_stack.back()->get()->function;
			
			
			while (function_test != nullptr && function_test != p_identifier->source_function && function_test->source_lambda != nullptr && !function_test->source_lambda->captures_indices.has(p_identifier->name)) {
				function_test->source_lambda->captures_indices[p_identifier->name] = function_test->source_lambda->captures.size();
				function_test->source_lambda->captures.push_back(p_identifier);
				function_test = function_test->source_lambda->parent_function;
			}
		}
		return;
	}
	StringName name = p_identifier->name;
	p_identifier->source = GDScriptParser::IdentifierNode::UNDEFINED_SOURCE;
	
	
	Variant::Type builtin_type = GDScriptParser::get_builtin_type(name);
	if (builtin_type != Variant::OBJECT && builtin_type < Variant::VARIANT_MAX) {
		if (can_be_builtin) {
			p_identifier->set_datatype(make_builtin_meta_type(builtin_type));
			return;
		} else {
			push_error(R"(Builtin type cannot be used as a name on its own.)", p_identifier);
		}