`Object::notification()` doesn't fully respect its `p_reversed` parameter

[kleonc]

Godot version

3.3.3.stable, 4.0.dev (c97afc0)

System information

N/A

Issue description

Object::notification() always calls _notification() in order:

1. For built-in classes - possibly in reversed order according to p_reversed parameter.
2. For scripts - always in the same order.
3. For extensions (4.0 only) - always in the same order.

Relevant source code:

godot/core/object/object.cpp

Lines 840 to 850 in c97afc0

	void Object::notification(int p_notification, bool p_reversed) {
	_notificationv(p_notification, p_reversed);
	if (script_instance) {
	script_instance->notification(p_notification);
	}
	if (_extension && _extension->notification) {
	_extension->notification(_extension_instance, p_notification);
	}
	}

So for example for an object b of type B with inheritance:
Object < Node < A (gdscript) < B (gdscript)
here's a comparison of the current behavior and what I'd say is expected behavior:

call	current call order	expected call order
b.notification(12345, false)	1. Object::_notification 2. Node::_notification 3. B::_notification 4. A::_notification	1. Object::_notification 2. Node::_notification 3. A::_notification 4. B::_notification
b.notification(12345, true)	1. Node::_notification 2. Object::_notification 3. B::_notification 4. A::_notification	1. B::_notification 2. A::_notification 3. Node::_notification 4. Object::_notification

Also current notification()'s description in the docs is misleading because reversed parameter currently doesn't affect the order of execution of in-script _notification() overrides.

Steps to reproduce

Run such script:

tool
extends EditorScript

func _run() -> void:
	var b := B.new()
	for reversed in [ false, true ]:
		print("reversed = %s" % [ reversed ])
		b.notification(12345, reversed)

class A:
	func _notification(what: int) -> void:
		if what == 12345:
			print("A")
		
class B extends A:
	func _notification(what: int) -> void:
		if what == 12345:
			print("B")

Output:

reversed = False
B
A
reversed = True
B
A

Minimal reproduction project

Just run script above.