### 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)


variable_type = return_type;
				variable_type.type_source = list_type.type_source;
			} else if (!list_type.is_hard_type()) {
				variable_type.kind = GDScriptParser::DataType::VARIANT;
			} else {
				push_error(vformat(R"(Unable to iterate on object of type "%s".)", list_type.to_string()), p_for->list);
			}
		} else if (list_type.builtin_type == Variant::ARRAY || list_type.builtin_type == Variant::DICTIONARY || !list_type.is_hard_type()) {
			variable_type.kind = GDScriptParser::DataType::VARIANT;
		} else {
			push_error(vformat(R"(Unable to iterate on value of type "%s".)", list_type.to_string()), p_for->list);
		}
	}
	if (p_for->variable) {
		p_for->variable->set_datatype(variable_type);
	}
	resolve_suite(p_for->loop);
	p_for->set_datatype(p_for->loop->get_datatype());
#ifdef DEBUG_ENABLED
	if (p_for->variable) {
		is_shadowing(p_for->variable, R"("for" iterator variable)");
	}
#endif
}
void GDScriptAnalyzer::resolve_while(GDScriptParser::WhileNode *p_while) {
	resolve_node(p_while->condition, false);
	resolve_suite(p_while->loop);
	p_while->set_datatype(p_while->loop->get_datatype());
}
void GDScriptAnalyzer::resolve_assert(GDScriptParser::AssertNode *p_assert) {