Deprecate torch.triangular_solve (#63570)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63570
There is a use of `at::triangular_solve_out` in the file
`torch/csrc/jit/tensorexpr/external_functions.cpp` that I have not dared
to move to `at::linalg_solve_triangular_out`.
**Deprecation note:**
This PR deprecates the `torch.triangular_solve` function in favor of
`torch.linalg.solve_triangular`. An upgrade guide is added to the
documentation for `torch.triangular_solve`.
Note that it DOES NOT remove `torch.triangular_solve`, but
`torch.triangular_solve` will be removed in a future PyTorch release.
cc jianyuh nikitaved pearu mruberry walterddr IvanYashchuk xwang233 Lezcano
Test Plan: Imported from OSS
Reviewed By: mruberry
Differential Revision: D32618035
Pulled By: anjali411
fbshipit-source-id: 0bfb48eeb6d96eff3e96e8a14818268cceb93c83
