### 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 (valid) {
				p_subscript->is_constant = true;
				p_subscript->reduced_value = value;
				result_type = type_from_variant(value, p_subscript);
			}
		} else if (base_type.is_variant() || !base_type.is_hard_type()) {
			valid = !base_type.is_pseudo_type || p_can_be_pseudo_type;
			result_type.kind = GDScriptParser::DataType::VARIANT;
			if (base_type.is_variant() && base_type.is_hard_type() && base_type.is_meta_type && base_type.is_pseudo_type) {
				
				String enum_name;
				if (p_subscript->base->type == GDScriptParser::Node::IDENTIFIER) {
					enum_name = String(static_cast<GDScriptParser::IdentifierNode *>(p_subscript->base)->name) + ENUM_SEPARATOR + String(p_subscript->attribute->name);
				}
				if (CoreConstants::is_global_enum(enum_name)) {
					result_type = make_global_enum_type(enum_name, StringName());
				} else {
					valid = false;
					mark_node_unsafe(p_subscript);
				}
			} else {
				mark_node_unsafe(p_subscript);
			}
		} else {
			reduce_identifier_from_base(p_subscript->attribute, &base_type);
			GDScriptParser::DataType attr_type = p_subscript->attribute->get_datatype();
			if (attr_type.is_set()) {
				valid = !attr_type.is_pseudo_type || p_can_be_pseudo_type;
				result_type = attr_type;
				p_subscript->is_constant = p_subscript->attribute->is_constant;