Sub-resource id changes for no reason

[KoBeWi]

Godot version:
3.2 beta1

Issue description:
Could be another case of #30538, dunno (judging from #30538 (comment), it could be revived). I noticed that sometimes my resources still shuffle, even though it should be fixed. I just
found a test case that reproduces it 100%, so I think it's time to open an issue about it.

Steps to reproduce:

1. Open the reproduction project
2. Open "Nodes/UI/InGame/UI.tscn" scene
3. Open the same scene in some external text editor
4. Go to line 162. Notice the animation has id=16
5. Save the scene in Godot
6. Animation is now id=15

This always happens.

Minimal reproduction project:
ReproductionProject.zip
(this is a dump of my game with irrelevant parts removed)

[chiguireitor]

Have this issue too, today i compiled tools beta2, will keep an eye on this issue as it affects mergability of different branches of my project.

[KoBeWi]

Not sure if related, but AnimatedSprite's animations can move around.

I'll add this issue to 3.2 milestone, because similar pointless changes happen A LOT (and the other similar issue had 3.2 too). While you can, heh, just discard these changes, there's always a risk of discarding your work and it's... uncomfortable.

[akien-mga]

Duplicate of #22226.