Use torch::from_blob instead of shareExternalPointer, nits (#25973)
Summary:
The main part is to switch at::Tensor creation from usage of `torch::empty(torch::IntArrayRef(...))->ShareExternalPointer(...) to torch::from_blob(...)`
Removed explicit set of `device CPU` as `at::TensorOptions` by default `device CPU`
And renaming of local variables removing `input` prefix to make them shorter
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25973
Differential Revision: D17356837
Pulled By: IvanKobzarev
fbshipit-source-id: 679e099b8aebd787dbf8ed422dae07a81243e18f
