Revert "Cleanup scatter-related code (#103074)"
This reverts commit 88aea179e379c743764e148adb86f1a320f0a299.
Reverted https://github.com/pytorch/pytorch/pull/103074 on behalf of https://github.com/izaitsevfb due to Breaks internal builds, see D46629742, symbol not found: scatter_add_expanded_index_stub ([comment](https://github.com/pytorch/pytorch/pull/103074#issuecomment-1587823954))
