add function to get NCCL version for logging (#26583)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26583
Adds a function that uses the nccl api to get the version code. Converts it to a readable version. Will be
used for logging NCCL version in exception messages.
Test Plan: See above
Differential Revision: D17473200
fbshipit-source-id: 4881ed5221b397f2f967262668c2b376b6bf3c64
