### 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)


ERR_FAIL_COND_MSG(p_node == nullptr, "Trying to resolve type of a null node.");
	switch (p_node->type) {
		case GDScriptParser::Node::NONE:
			break; 
		case GDScriptParser::Node::CLASS:
			if (OK == resolve_class_inheritance(static_cast<GDScriptParser::ClassNode *>(p_node), true)) {
				resolve_class_interface(static_cast<GDScriptParser::ClassNode *>(p_node), true);
				resolve_class_body(static_cast<GDScriptParser::ClassNode *>(p_node), true);
			}
			break;
		case GDScriptParser::Node::CONSTANT:
			resolve_constant(static_cast<GDScriptParser::ConstantNode *>(p_node), true);
			break;
		case GDScriptParser::Node::FOR:
			resolve_for(static_cast<GDScriptParser::ForNode *>(p_node));
			break;
		case GDScriptParser::Node::IF:
			resolve_if(static_cast<GDScriptParser::IfNode *>(p_node));
			break;
		case GDScriptParser::Node::SUITE:
			resolve_suite(static_cast<GDScriptParser::SuiteNode *>(p_node));
			break;
		case GDScriptParser::Node::VARIABLE:
			resolve_variable(static_cast<GDScriptParser::VariableNode *>(p_node), true);