### Godot version

4.2.beta.custom_build [51f81e1c8]

### System information

macOS 11.0+

### Issue description

I could sense a recent merging of a few pull requests on here:

<img width="865" alt="image" src="https://github.com/godotengine/godot/assets/1129695/1cf7d144-a4d2-4514-abca-1405222e702a">

This bug has the following related merges as the most recent ones:

https://github.com/godotengine/godot/pull/80813
https://github.com/godotengine/godot/pull/80939

The pull requests are for reviving onion-skinning capabilities, but this causes a minor unexpected result (see Steps to reproduce)



### Steps to reproduce

## A. Use 4.2.beta.custom_build [51f81e1c8]

1. Obtain the attached minimal reproduction project
2. Select the AnimationPlayer node
<img width="1468" alt="image" src="https://github.com/godotengine/godot/assets/1129695/ca16d7a6-7690-45b4-b8f9-b12fded64ca4">
3. In the Animation panel, click "Edit" to find your shortcuts for "Go to Next Step" and "Go to Previous Step"
<img width="410" alt="image" src="https://github.com/godotengine/godot/assets/1129695/a708e196-2eb9-42ea-bf0e-fd0aa88a9e60">
4. Use the shortcuts to spam go back and forth the animation

Expected result: animation goes smoothly

https://github.com/godotengine/godot/assets/1129695/c24c498c-7f77-4cc9-a1c9-a1627d89c58b



Actual result: animation jumps crazily


https://github.com/godotengine/godot/assets/1129695/947bf5b4-a0ab-42d4-bb5b-201800b4bdc6


https://github.com/godotengine/godot/assets/1129695/65303cd0-8c2d-4a35-9d16-c94752ac2e3a




## B. My successful yet unverified fix attempt on 4.2.beta.custom_build [51f81e1c8]

Either by:

<img width="831" alt="image" src="https://github.com/godotengine/godot/assets/1129695/80d167ae-27e7-4ec4-a4c9-ffc7adc0353f">


Or by:

<img width="806" alt="image" src="https://github.com/godotengine/godot/assets/1129695/2bae8697-8ef3-48dc-9f0a-2b5fe568ed43">


I don't see any negative impact on Onion Skinning or other functions by the above fix attempt, but I am not sure, I need someone to help me verify this.



### Minimal reproduction project

[gd_anim_unittest_1.zip](https://github.com/godotengine/godot/files/12909805/gd_anim_unittest_1.zip)






DEV_ASSERT(p_step_offset != 0);
	DEV_ASSERT(onion.captures_valid[p_capture_idx]);
	RID root_vp = get_tree()->get_root()->get_viewport_rid();
	RS::get_singleton()->viewport_set_active(onion.captures[p_capture_idx], true);
	RS::get_singleton()->viewport_set_parent_viewport(root_vp, onion.captures[p_capture_idx]);
	RS::get_singleton()->draw(false);
	RS::get_singleton()->viewport_set_active(onion.captures[p_capture_idx], false);
	int last_step_offset = onion.future ? onion.steps : 0;
	if (p_step_offset < last_step_offset) {
		_prepare_onion_layers_2_step_prepare(p_step_offset + 1, p_capture_idx + 1);
	} else {
		_prepare_onion_layers_2_epilog();
	}
}
void AnimationPlayerEditor::_prepare_onion_layers_2_epilog() {
	
	RID root_vp = get_tree()->get_root()->get_viewport_rid();
	RS::get_singleton()->viewport_set_parent_viewport(root_vp, RID());
	RS::get_singleton()->viewport_attach_to_screen(root_vp, onion.temp.screen_rect, DisplayServer::MAIN_WINDOW_ID);
	RS::get_singleton()->viewport_set_update_mode(root_vp, RS::VIEWPORT_UPDATE_WHEN_VISIBLE);