### 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)


case GDScriptParser::ClassNode::Member::VARIABLE: {
					if (is_base && (!base.is_meta_type || member.variable->is_static)) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = member.variable->is_static ? GDScriptParser::IdentifierNode::STATIC_VARIABLE : GDScriptParser::IdentifierNode::MEMBER_VARIABLE;
						p_identifier->variable_source = member.variable;
						member.variable->usages += 1;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::SIGNAL: {
					if (is_base && !base.is_meta_type) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_SIGNAL;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::FUNCTION: {
					if (is_base && (!base.is_meta_type || member.function->is_static)) {
						p_identifier->set_datatype(make_callable_type(member.function->info));
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::CLASS: {
					reduce_identifier_from_base_set_class(p_identifier, member.get_datatype());
					return;
				}
				default: {
					
				}
			}