Torchelastic: add multiprocessing tests to ci/cd (#56842)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56842
Add elastic multiprocessing test to ci/cd
Test Plan: buck test mode/opt-tsan //caffe2/test/distributed/elastic/multiprocessing/... -- --run-disabled
Reviewed By: wilson100hong
Differential Revision: D27982226
fbshipit-source-id: 1b4e6f1a20867a6aa7ca409e280fdb04e8db198b
