### 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)

Playback &c = playback;
	bool seeked = c.seeked; 
	if (p_delta != 0) {
		c.seeked = false;
	}
	
	float blend = 1.0;
	for (List<Blend>::Element *E = c.blend.front(); E; E = E->next()) {
		Blend &b = E->get();
		blend = MAX(0, blend - b.blend_left);
		b.blend_left = MAX(0, b.blend_left - Math::absf(speed_scale * p_delta) / b.blend_time);
	}
	
	_process_playback_data(c.current, p_delta, blend, seeked, p_started, true);
	
	if (end_reached) {
		playback.blend.clear();
		return;
	}
	List<List<Blend>::Element *> to_erase;
	for (List<Blend>::Element *E = c.blend.front(); E; E = E->next()) {
		Blend &b = E->get();
		if (b.blend_left <= 0) {
			to_erase.push_back(E);