### 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 (p_await->to_await == nullptr) {
		GDScriptParser::DataType await_type;
		await_type.kind = GDScriptParser::DataType::VARIANT;
		p_await->set_datatype(await_type);
		return;
	}
	if (p_await->to_await->type == GDScriptParser::Node::CALL) {
		reduce_call(static_cast<GDScriptParser::CallNode *>(p_await->to_await), true);
	} else {
		reduce_expression(p_await->to_await);
	}
	GDScriptParser::DataType await_type = p_await->to_await->get_datatype();
	
	if (await_type.is_hard_type() && await_type.kind == GDScriptParser::DataType::BUILTIN && await_type.builtin_type == Variant::SIGNAL) {
		await_type.kind = GDScriptParser::DataType::VARIANT;
		await_type.type_source = GDScriptParser::DataType::UNDETECTED;
	} else if (p_await->to_await->is_constant) {
		p_await->is_constant = p_await->to_await->is_constant;
		p_await->reduced_value = p_await->to_await->reduced_value;
	}
	await_type.is_coroutine = false;
	p_await->set_datatype(await_type);
#ifdef DEBUG_ENABLED
	GDScriptParser::DataType to_await_type = p_await->to_await->get_datatype();
	if (!to_await_type.is_coroutine && !to_await_type.is_variant() && to_await_type.builtin_type != Variant::SIGNAL) {
		parser->push_warning(p_await, GDScriptWarning::REDUNDANT_AWAIT);
	}
#endif
}
void GDScriptAnalyzer::reduce_binary_op(GDScriptParser::BinaryOpNode *p_binary_op) {