### 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 (node != nullptr) {
						Ref<GDScript> scr = node->get_script();
						if (scr.is_valid()) {
							Ref<GDScriptParserRef> singl_parser = get_parser_for(scr->get_script_path());
							if (singl_parser.is_valid()) {
								Error err = singl_parser->raise_status(GDScriptParserRef::INHERITANCE_SOLVED);
								if (err == OK) {
									result = type_from_metatype(singl_parser->get_parser()->head->get_datatype());
								}
							}
						}
					}
				}
			}
			result.is_constant = true;
			p_identifier->set_datatype(result);
			return;
		}
	}
	if (CoreConstants::is_global_constant(name)) {
		int index = CoreConstants::get_global_constant_index(name);
		StringName enum_name = CoreConstants::get_global_constant_enum(index);
		int64_t value = CoreConstants::get_global_constant_value(index);
		if (enum_name != StringName()) {
			p_identifier->set_datatype(make_global_enum_type(enum_name, StringName(), false));
		} else {
			p_identifier->set_datatype(type_from_variant(value, p_identifier));
		}
		p_identifier->is_constant = true;
		p_identifier->reduced_value = value;