[NCCL] Init dummy NCCL comms in constructor (#65173)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65173
Initializes dummy NCCL communicators in constructor for a basic health
check that communicators can be initialized prior to launching the first
collective.
After successful init, we immediately use `ncclCommAbort` to destroy these
communicators to ensure they don't interfere with regular communicator creation
during collectives.
Test Plan: CI
Reviewed By: pritamdamania87
Differential Revision: D31005792
fbshipit-source-id: c2c582dee25a098361ead6ef03f541e7833c606b
