### 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)


current_enum = prev_enum;
					if (!member.enum_value.custom_value->is_constant) {
						push_error(R"(Enum values must be constant.)", member.enum_value.custom_value);
					} else if (member.enum_value.custom_value->reduced_value.get_type() != Variant::INT) {
						push_error(R"(Enum values must be integers.)", member.enum_value.custom_value);
					} else {
						member.enum_value.value = member.enum_value.custom_value->reduced_value;
						member.enum_value.resolved = true;
					}
				} else {
					check_class_member_name_conflict(p_class, member.enum_value.identifier->name, member.enum_value.parent_enum);
					if (member.enum_value.index > 0) {
						const GDScriptParser::EnumNode::Value &prev_value = member.enum_value.parent_enum->values[member.enum_value.index - 1];
						resolve_class_member(p_class, prev_value.identifier->name, member.enum_value.identifier);
						member.enum_value.value = prev_value.value + 1;
					} else {
						member.enum_value.value = 0;
					}
					member.enum_value.resolved = true;
				}
				
				member.enum_value.parent_enum->values.set(member.enum_value.index, member.enum_value);
				member.enum_value.identifier->set_datatype(make_enum_type(UNNAMED_ENUM, p_class->fqcn, false));
			} break;
			case GDScriptParser::ClassNode::Member::CLASS:
				check_class_member_name_conflict(p_class, member.m_class->identifier->name, member.m_class);
				
				if (!member.m_class->base_type.is_resolving()) {
					resolve_class_inheritance(member.m_class, p_source);
				}