Revert "[C10D] Introduce C++ side Collective Callbacks. (#110307)"
This reverts commit 359336e3e9a0f67974e53805b5207fbbbc149490.
Reverted https://github.com/pytorch/pytorch/pull/110307 on behalf of https://github.com/wconstab due to this sits on top of another PR https://github.com/pytorch/pytorch/pull/111072 that needs to be reverted due to internal release testing failure / multisect blame ([comment](https://github.com/pytorch/pytorch/pull/110307#issuecomment-1764910301))
