Added linalg.eigh, linalg.eigvalsh (#45526)
Summary:
This PR adds `torch.linalg.eigh`, and `torch.linalg.eigvalsh` for NumPy compatibility.
The current `torch.symeig` uses (on CPU) a different LAPACK routine than NumPy (`syev` vs `syevd`). Even though it shouldn't matter in practice, `torch.linalg.eigh` uses `syevd` (as NumPy does).
Ref https://github.com/pytorch/pytorch/issues/42666
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45526
Reviewed By: gchanan
Differential Revision: D25022659
Pulled By: mruberry
fbshipit-source-id: 3676b77a121c4b5abdb712ad06702ac4944e900a
