Add arcosh, arcsinh and arctanh to unary ops (#38388)
Summary:
This PR aims to add `arcosh`, `arcsinh` and `arctanh` support. Please see issue https://github.com/pytorch/pytorch/issues/38349 for more details.
**TODOs:**
* [x] Add test cases for `arcosh`, `arcsinh` and `arctanh`. (need help)
* [x] Overload ops if `std::op` does not work with `thrust::complex` types (like for `sinh`, `cosh`).
Note: `std::acosh, std::asinh, std::atanh` do not support `thrust::complex` types. Added support for complex types for these 3 ops (`arccosh, arcsinh, arctanh`)
cc: mruberry
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38388
Differential Revision: D21882055
Pulled By: mruberry
fbshipit-source-id: d334590b47c5a89e491a002c3e41e6ffa89000e3
