### 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)


for (GDScriptParser::AnnotationNode *&E : member.signal->annotations) {
					resolve_annotation(E);
					E->apply(parser, member.signal);
				}
			} break;
			case GDScriptParser::ClassNode::Member::ENUM: {
				check_class_member_name_conflict(p_class, member.m_enum->identifier->name, member.m_enum);
				member.m_enum->set_datatype(resolving_datatype);
				GDScriptParser::DataType enum_type = make_enum_type(member.m_enum->identifier->name, p_class->fqcn, true);
				const GDScriptParser::EnumNode *prev_enum = current_enum;
				current_enum = member.m_enum;
				Dictionary dictionary;
				for (int j = 0; j < member.m_enum->values.size(); j++) {
					GDScriptParser::EnumNode::Value &element = member.m_enum->values.write[j];
					if (element.custom_value) {
						reduce_expression(element.custom_value);
						if (!element.custom_value->is_constant) {
							push_error(R"(Enum values must be constant.)", element.custom_value);
						} else if (element.custom_value->reduced_value.get_type() != Variant::INT) {
							push_error(R"(Enum values must be integers.)", element.custom_value);
						} else {
							element.value = element.custom_value->reduced_value;
							element.resolved = true;
						}
					} else {
						if (element.index > 0) {
							element.value = element.parent_enum->values[element.index - 1].value + 1;
						} else {
							element.value = 0;