### 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)






uint32_t next_capture_idx = p_capture_idx;
	if (p_step_offset == 0) {
		
		if (!onion.force_white_modulate) {
			onion.capture.material->set_shader_parameter("dir_color", EDITOR_GET("editors/animation/onion_layers_future_color"));
		}
	} else {
		Ref<Animation> anim = player->get_animation(player->get_assigned_animation());
		double pos = onion.temp.anim_player_position + p_step_offset * anim->get_step();
		bool valid = anim->get_loop_mode() != Animation::LOOP_NONE || (pos >= 0 && pos <= anim->get_length());
		onion.captures_valid[p_capture_idx] = valid;
		if (valid) {
			player->seek(pos, true, true);
			OS::get_singleton()->get_main_loop()->process(0);
			
			
			callable_mp(this, &AnimationPlayerEditor::_prepare_onion_layers_2_step_capture).bind(p_step_offset, p_capture_idx).call_deferred();
			return;
		} else {
			next_capture_idx++;
		}
	}
	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, next_capture_idx);
	} else {
		_prepare_onion_layers_2_epilog();
	}
}
void AnimationPlayerEditor::_prepare_onion_layers_2_step_capture(int p_step_offset, uint32_t p_capture_idx) {