### Godot version

4.2 RC2

### System information

Any

### Issue description

AnimationMixer separates the accuracy of how discrete keys are retrieved when seeking between internal seeking and external seeking. FYI: https://github.com/godotengine/godot/pull/80708.

Since AnimationPlayer currently treats everything as an internal seek, so it needs to propagate the external seek information.

### Steps to reproduce

Seek AnimationTrackEditor

### Minimal reproduction project

[gd_anim_unittest_1.zip](https://github.com/godotengine/godot/files/13492063/gd_anim_unittest_1.zip)

}
	if (c.assigned != name) { 
		c.current.pos = p_from_end ? c.current.from->animation->get_length() : 0;
		c.assigned = name;
		emit_signal(SNAME("current_animation_changed"), c.assigned);
	} else {
		if (p_from_end && c.current.pos == 0) {
			
			c.current.pos = c.current.from->animation->get_length();
		} else if (!p_from_end && c.current.pos == c.current.from->animation->get_length()) {
			
			c.current.pos = 0;
		} else if (playing) {
			return;
		}
	}
	c.seeked = false;
	c.started = true;
	_set_process(true); 
	playing = true;
	emit_signal(SceneStringNames::get_singleton()->animation_started, c.assigned);
	if (is_inside_tree() && Engine::get_singleton()->is_editor_hint()) {
		return; 
	}
	StringName next = animation_get_next(p_name);
	if (next != StringName() && animation_set.has(next)) {
		queue(next);
	}
}
bool AnimationPlayer::is_playing() const {