Add docs for how we expose declarations in at:: to torch:: (#30760)
Summary:
This PR adds docs for how we expose declarations in `at::` to `torch::`, to make the semantics more clear.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30760
Differential Revision: D18833081
Pulled By: yf225
fbshipit-source-id: eff4d8815c67f681ce3a930ce99771cf2e55dbd9
