Fix 2 bugs with scale of position tracks in rest fixer

[lyuma]

Both bugs were related to how position animation tracks were adjusted in rest fixer.
First bug: motion scale is applied before subtracting the origin when applying bone roll
Second bug: armature scale was lost when converting basis to quaternion, leading an unscaled position offset to be added to the scaled origin.

The bug becomes evident in the test files attached to issue

• Remove Immutable Tracks import option breaks some character animations #90031
  especially after applying PR
• Apply "Remove Immutable Tracks" after post-import. #90064

[akien-mga]

Thanks!