### 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)


push_error(vformat(R"(Cannot assign a value of type %s to %s "%s" with specified type %s.)", initializer_type.to_string(), p_kind, p_assignable->identifier->name, specified_type.to_string()), p_assignable->initializer);
				}
			} else if (specified_type.has_container_element_type() && !initializer_type.has_container_element_type()) {
				mark_node_unsafe(p_assignable->initializer);
#ifdef DEBUG_ENABLED
			} else if (specified_type.builtin_type == Variant::INT && initializer_type.builtin_type == Variant::FLOAT) {
				parser->push_warning(p_assignable->initializer, GDScriptWarning::NARROWING_CONVERSION);
#endif
			}
		}
	}
	type.is_constant = is_constant;
	type.is_read_only = false;
	p_assignable->set_datatype(type);
}
void GDScriptAnalyzer::resolve_variable(GDScriptParser::VariableNode *p_variable, bool p_is_local) {
	static constexpr const char *kind = "variable";
	resolve_assignable(p_variable, kind);
#ifdef DEBUG_ENABLED
	if (p_is_local) {
		if (p_variable->usages == 0 && !String(p_variable->identifier->name).begins_with("_")) {
			parser->push_warning(p_variable, GDScriptWarning::UNUSED_VARIABLE, p_variable->identifier->name);
		} else if (p_variable->assignments == 0) {
			parser->push_warning(p_variable, GDScriptWarning::UNASSIGNED_VARIABLE, p_variable->identifier->name);
		}
		is_shadowing(p_variable->identifier, kind);
	}
#endif
}
void GDScriptAnalyzer::resolve_constant(GDScriptParser::ConstantNode *p_constant, bool p_is_local) {