### 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)


}
		if (!p_is_root && !p_is_await && return_type.is_hard_type() && return_type.kind == GDScriptParser::DataType::BUILTIN && return_type.builtin_type == Variant::NIL) {
			push_error(vformat(R"*(Cannot get return value of call to "%s()" because it returns "void".)*", p_call->function_name), p_call);
		}
#ifdef DEBUG_ENABLED
		if (p_is_root && return_type.kind != GDScriptParser::DataType::UNRESOLVED && return_type.builtin_type != Variant::NIL &&
				!(p_call->is_super && p_call->function_name == GDScriptLanguage::get_singleton()->strings._init)) {
			parser->push_warning(p_call, GDScriptWarning::RETURN_VALUE_DISCARDED, p_call->function_name);
		}
		if (method_flags.has_flag(METHOD_FLAG_STATIC) && !is_constructor && !base_type.is_meta_type && !(is_self && static_context)) {
			String caller_type = String(base_type.native_type);
			if (caller_type.is_empty()) {
				caller_type = base_type.to_string();
			}
			parser->push_warning(p_call, GDScriptWarning::STATIC_CALLED_ON_INSTANCE, p_call->function_name, caller_type);
		}
#endif 
		call_type = return_type;
	} else {
		bool found = false;
		
		if (base_type.kind == GDScriptParser::DataType::ENUM && base_type.is_meta_type) {
			if (base_type.builtin_type == Variant::DICTIONARY) {
				push_error(vformat(R"*(Enums only have Dictionary built-in methods. Function "%s()" does not exist for enum "%s".)*", p_call->function_name, base_type.enum_type), p_call->callee);
			} else {
				push_error(vformat(R"*(The native enum "%s" does not behave like Dictionary and does not have methods of its own.)*", base_type.enum_type), p_call->callee);
			}
		} else if (!p_call->is_super && callee_type != GDScriptParser::Node::NONE) { 
			GDScriptParser::IdentifierNode *callee_id;
			if (callee_type == GDScriptParser::Node::IDENTIFIER) {