adding sharding option to run_test.py (#45583)
Summary:
Added a sharding option to run_test.py to enable users to run a subset of the many tests. The new `--shard` argument takes in two integer values, `x` and `y`, where the larger value would denote the number of shards and the smaller value would denote which shard to run.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45583
Reviewed By: malfet
Differential Revision: D24083469
Pulled By: janeyx99
fbshipit-source-id: 1777bd7822c95b3bf37079deff9381c6f8eaf4cc
