[SR] Out variant for embedding_bag_byte_unpack
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77661
Add an out variant and wrapper in static runtime.
I just added the declaration with the others in `qembeddingbag.h` for now (rather than properly adding the out variant to the torch library). This can be fixed in a followup.
Differential Revision: [D36449840](https://our.internmc.facebook.com/intern/diff/D36449840/)
**NOTE FOR REVIEWERS**: This PR has internal Facebook specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D36449840/)!
Approved by: https://github.com/tenpercent
