Add a new HashSet template

* Intended to replace RBSet in most cases.
* Optimized for iteration speed

editor/animation_track_editor.cpp

@@ -5906,7 +5906,7 @@ void AnimationTrackEditor::_edit_menu_pressed(int p_option) {
 			undo_redo->create_action(TTR("Anim Add RESET Keys"));
 			Ref<Animation> reset = _create_and_get_reset_animation();
 			int reset_tracks = reset->get_track_count();
-			RBSet<int> tracks_added;
+			HashSet<int> tracks_added;
 
 			for (const KeyValue<SelectedKey, KeyInfo> &E : selection) {
 				const SelectedKey &sk = E.key;