Port CPU torch.geqrf to ATen (#56249)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56249
This PR ports `torch.geqrf` from TH to ATen. CUDA path will be
implemented in a follow-up PR.
With ATen port support for complex and batched inputs is added.
There were no correctness tests, they are
added in this PR and I added OpInfo for this operation.
We can implement the QR decomposition as a composition of geqrf and
orgqr (torch.linalg.householder_product).
Also we can implement the least squares solver with geqrf + ormqr +
trtrs. So it's useful to have this function renewed at least for the
internal code.
Resolves https://github.com/pytorch/pytorch/issues/24705
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D27907357
Pulled By: mruberry
fbshipit-source-id: 94e1806078977417e7903db76eab9d578305f585
