[PyTorch] Move TensorImpl::shallow_copy_and_detach to .cpp file (#48680)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48680
It seems a bit long to put into the header (and is virtual anyway).
ghstack-source-id: 117894350
Test Plan: CI
Reviewed By: bhosmer
Differential Revision: D25259848
fbshipit-source-id: e3eed1f2483fc3c1ff51459159bf3bfed9d6f363
