### 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)


void GDScriptAnalyzer::reduce_expression(GDScriptParser::ExpressionNode *p_expression, bool p_is_root) {
	
	if (p_expression == nullptr) {
		return;
	}
	if (p_expression->reduced) {
		
		return;
	}
	p_expression->reduced = true;
	switch (p_expression->type) {
		case GDScriptParser::Node::ARRAY:
			reduce_array(static_cast<GDScriptParser::ArrayNode *>(p_expression));
			break;
		case GDScriptParser::Node::ASSIGNMENT:
			reduce_assignment(static_cast<GDScriptParser::AssignmentNode *>(p_expression));
			break;
		case GDScriptParser::Node::AWAIT:
			reduce_await(static_cast<GDScriptParser::AwaitNode *>(p_expression));
			break;
		case GDScriptParser::Node::BINARY_OPERATOR:
			reduce_binary_op(static_cast<GDScriptParser::BinaryOpNode *>(p_expression));
			break;
		case GDScriptParser::Node::CALL:
			reduce_call(static_cast<GDScriptParser::CallNode *>(p_expression), false, p_is_root);
			break;
		case GDScriptParser::Node::CAST:
			reduce_cast(static_cast<GDScriptParser::CastNode *>(p_expression));
			break;
		case GDScriptParser::Node::DICTIONARY: