[3.x] SpriteFrames: Sort animations alphabetically

[akien-mga]

• Fixes Godot keeps rearranging scene animation frames #62143.

Previously they would be serialized in the order they come with in Map. So when adding a new animation, it would be added at the end of the Map in the current process, and thus saved at the last element in the array in the .tscn. But when loading the scene in a new process, the Map could be reordered as it doesn't depend on the serialized array.

This is only used for (de)serialization from scene/res files so I think the performance impact of having to sort the StringNames is minimal.

The unwanted reordering doesn't seem to happen in master but I'll make a PR anyway to force alphabetical ordering, and remove the obsolete frames property.

3.x version of #62978.

[kleonc]

Makes sense and all looks good.

Since both for editor and for serializing alphabetical ordering is desired I wonder whether the internal storage of SpriteFrames could be just changed from map to ordered map. If the lookup times wouldn't be worse then it should be fine to do so? 🤔 And after such change we could remove all these sortings accross the editor/serialization. But in any case that's for potential another PR.

[akien-mga]

Yeah I thought about that too but I noticed that e.g. in AnimationPlayer it's also using a lot of Map<StringName, SomeCustomStruct>.

Might be worth discussing on chat and see if some general rules can be figured out to establish when it's worth it to used OrderedHashMap directly, or when it's preferred to keep it unordered and just sort where needed. In master we could maybe get some kind of way to get an iterator that goes through StringName keys ordered to simplify such code.