Implement hstack, vstack, dstack (#42799)
Summary:
Related to https://github.com/pytorch/pytorch/issues/38349
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42799
Reviewed By: izdeby
Differential Revision: D23140704
Pulled By: mruberry
fbshipit-source-id: 6a36363562c50d0abce87021b84b194bb32825fb
