### 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)


}
						element.resolved = true;
					}
					enum_type.enum_values[element.identifier->name] = element.value;
					dictionary[String(element.identifier->name)] = element.value;
				}
				current_enum = prev_enum;
				dictionary.make_read_only();
				member.m_enum->set_datatype(enum_type);
				member.m_enum->dictionary = dictionary;
				
				for (GDScriptParser::AnnotationNode *&E : member.m_enum->annotations) {
					resolve_annotation(E);
					E->apply(parser, member.m_enum);
				}
			} break;
			case GDScriptParser::ClassNode::Member::FUNCTION:
				for (GDScriptParser::AnnotationNode *&E : member.function->annotations) {
					resolve_annotation(E);
					E->apply(parser, member.function);
				}
				resolve_function_signature(member.function, p_source);
				break;
			case GDScriptParser::ClassNode::Member::ENUM_VALUE: {
				member.enum_value.identifier->set_datatype(resolving_datatype);
				if (member.enum_value.custom_value) {
					check_class_member_name_conflict(p_class, member.enum_value.identifier->name, member.enum_value.custom_value);
					const GDScriptParser::EnumNode *prev_enum = current_enum;
					current_enum = member.enum_value.parent_enum;
					reduce_expression(member.enum_value.custom_value);