Added linalg.solve (#48456)
Summary:
This PR adds `torch.linalg.solve`.
`linalg_solve_out` uses in-place operations on the provided result tensor.
I modified `apply_solve` to accept tensor of Int instead of std::vector, that way we can write a function similar to `linalg_solve_out` but removing the error checks and device memory synchronization.
In comparison to `torch.solve` this routine accepts 1-dimensional tensors and batches of 1-dim tensors for the right-hand-side term. `torch.solve` requires it to be at least 2-dimensional.
Ref. https://github.com/pytorch/pytorch/issues/42666
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48456
Reviewed By: izdeby
Differential Revision: D25562222
Pulled By: mruberry
fbshipit-source-id: a9355c029e2442c2e448b6309511919631f9e43b
