### 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 (const KeyValue<StringName, int64_t> &E : p_type.enum_values) {
		if (E.value == p_value) {
			return true;
		}
	}
	return false;
}
#endif
void GDScriptAnalyzer::update_const_expression_builtin_type(GDScriptParser::ExpressionNode *p_expression, const GDScriptParser::DataType &p_type, const char *p_usage, bool p_is_cast) {
	if (p_expression->get_datatype() == p_type) {
		return;
	}
	if (p_type.kind != GDScriptParser::DataType::BUILTIN && p_type.kind != GDScriptParser::DataType::ENUM) {
		return;
	}
	GDScriptParser::DataType expression_type = p_expression->get_datatype();
	bool is_enum_cast = p_is_cast && p_type.kind == GDScriptParser::DataType::ENUM && p_type.is_meta_type == false && expression_type.builtin_type == Variant::INT;
	if (!is_enum_cast && !is_type_compatible(p_type, expression_type, true, p_expression)) {
		push_error(vformat(R"(Cannot %s a value of type "%s" as "%s".)", p_usage, expression_type.to_string(), p_type.to_string()), p_expression);
		return;
	}
	GDScriptParser::DataType value_type = type_from_variant(p_expression->reduced_value, p_expression);