High: Core: Modify the v2 digest algorithm so that some fields are sorted

Due to the way the diff works, modified fields appear at the end
If the performance of this change is almost as bad as v1, then
we might need to modify the diff format to include all fields of
modified objects so we really can drop the sorting.

Mercurial revision: 258b56eb775c663e2e6f7d0a92de0588080e3afa