Add Batch-Updating Parameter Server Example to CI Tests (#46510)
Summary:
Resolves one item in https://github.com/pytorch/pytorch/issues/46321
This PR sets up DistExamplesTest which will be used as the class to implement future tests for examples. This class is run as part of CI tests. It also creates a dist_examples folder and includes the [batch server example](https://github.com/pytorch/examples/blob/master/distributed/rpc/batch/parameter_server.py) which is slightly modified to allow to be tested.
Run test:
pytest test/distributed/rpc/test_tensorpipe_agent.py -k test_batch_updating_parameter_server -vs
pytest test/distributed/rpc/test_process_group_agent.py -k test_batch_updating_parameter_server -vs
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46510
Reviewed By: mrshenli
Differential Revision: D24379296
Pulled By: H-Huang
fbshipit-source-id: 1c102041e338b022b7a659a51894422addc0e06f
