[gloo] change ProcessGroupGlooAsyncTest to use gtest (#42313)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42313
Changes the tests in `ProcessGroupGlooAsyncTest.cpp` to use the Gtest testing framework.
Reviewed By: malfet
Differential Revision: D22821577
fbshipit-source-id: 326b24a334ae84a16434d0d5ef27d16ba4b90d5d
