Root of the issue is that BKE_object_eval_boundbox (that ports back
evaluated bbox to orig object during active depsgraph evaluation) is
only called when object's geometry actually is evaluated.

However, with new undo, often Object itself can be changed by undo,
without requiring its geometry to be re-evaluated, which was leading to
the evaluated bbox not being copied back into orig object anymore.

Fixing that by moving bbox copying-to-orig code into
BKE_object_sync_to_original instead, which is always executed when
object is evaluated (as hinted by the comment above
BKE_object_eval_boundbox actually).

Also allows to cleanup code for armature eval, apparently.