### 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)


result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
		result.kind = GDScriptParser::DataType::BUILTIN;
		result.builtin_type = Variant::BOOL;
	} else if (left_type.is_variant() || right_type.is_variant()) {
		
		result.kind = GDScriptParser::DataType::VARIANT;
		mark_node_unsafe(p_binary_op);
	} else if (p_binary_op->variant_op < Variant::OP_MAX) {
		bool valid = false;
		result = get_operation_type(p_binary_op->variant_op, left_type, right_type, valid, p_binary_op);
		if (!valid) {
			push_error(vformat(R"(Invalid operands "%s" and "%s" for "%s" operator.)", left_type.to_string(), right_type.to_string(), Variant::get_operator_name(p_binary_op->variant_op)), p_binary_op);
		} else if (!result.is_hard_type()) {
			mark_node_unsafe(p_binary_op);
		}
	} else {
		ERR_PRINT("Parser bug: unknown binary operation.");
	}
	p_binary_op->set_datatype(result);
}
#ifdef SUGGEST_GODOT4_RENAMES
const char *get_rename_from_map(const char *map[][2], String key) {
	for (int index = 0; map[index][0]; index++) {
		if (map[index][0] == key) {
			return map[index][1];
		}
	}
	return nullptr;
}
const char *check_for_renamed_identifier(String identifier, GDScriptParser::Node::Type type) {