Remove most references to rockset:
* replace comments and docs with a generic "backend database"
* Delete `upload_to_rockset`, so we no longer need to install the package.
* Do not upload perf stats to rockset as well (we should be completely on DynamoDB now right @huydhn?)
According to VSCode, it went from 41 -> 7 instances of "rockset" in the repo
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139922
Approved by: https://github.com/huydhn, https://github.com/ZainRizvi