Skeleton rest fixer: Apply orthonormalized scale to anims

[lyuma]

Adjust the logic for position and scale animation tracks in the Apply Node Transforms case To match how we adjust bone pose/rest, use basis.orthonormalized() for parentless bones.

Fixes #91893
Cc @TokageItLab @fire

[TokageItLab]

For now, I think it is fine about this fix. My only concern for now about remove immutable tracks is:

However, apart from this, I am wondering if the past remove immutable tracks are dead code due to the #90064 change, are they still being used for something other than Skeleton?

If we need it for something other than Skeleton, we need to consider whether that code can be commonized with what we added in #90064.

P.S. BTW, I will send another proposal later for bones which have own scales.

[akien-mga]

Thanks!