### 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)

return (is_playing() ? playback.assigned : "");
}
void AnimationPlayer::set_assigned_animation(const String &p_animation) {
	if (is_playing()) {
		float speed = playback.current.speed_scale;
		play(p_animation, -1.0, speed, signbit(speed));
	} else {
		ERR_FAIL_COND_MSG(!animation_set.has(p_animation), vformat("Animation not found: %s.", p_animation));
		playback.current.pos = 0;
		playback.current.from = &animation_set[p_animation];
		playback.assigned = p_animation;
		emit_signal(SNAME("current_animation_changed"), playback.assigned);
	}
}
String AnimationPlayer::get_assigned_animation() const {
	return playback.assigned;
}
void AnimationPlayer::pause() {
	_stop_internal(false, false);
}
void AnimationPlayer::stop(bool p_keep_state) {
	_stop_internal(true, p_keep_state);
}
void AnimationPlayer::set_speed_scale(float p_speed) {
	speed_scale = p_speed;
}
float AnimationPlayer::get_speed_scale() const {