[5/n][torch/elastic][upstream] Move torchelastic/agent to torch/distributed/elastic/agent (#54343)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54343
Move torchelastic/agent to torch/distributed/elastic/agent
Test Plan:
buck test mode/dev-nosan //pytorch/elastic/torchelastic/...
buck test mode/dev-nosan //caffe2/test/distributed/elastic/agent/server/test/...
Reviewed By: kiukchung, wilson100hong
Differential Revision: D27173271
fbshipit-source-id: 26761acc3f962af2afffcc3c7a237f3b6d65e531
