Support bf16 searchsort op (#99426)
Per title, needed to unblock bf16 for an ads tformer workload
Differential Revision: [D45088972](https://our.internmc.facebook.com/intern/diff/D45088972/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99426
Approved by: https://github.com/XilunWu
