[1/n][torch/elastic][upstream] Move torchelastic/rendezvous to torch/distributed/rendezvous (#53172)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53172
Pull Request resolved: https://github.com/pytorch/elastic/pull/141
Upstreams two modules to torch:
1. `torchelastic.rendezvous`
2. `torchelastic.utils`
These modules were chosen as `[1/n]` since they are the leaf modules in torchelastic.
==== NOTES: ====
1. I'm disabling etcd_rendezvous and etcd_server tests in CIRCLECI for the moment since I need to edit the test dockers to contain the etcd server binary (there's 4-5 test dockers - one for each platform so this is going to take some time for me to set up the environments and test) - T85992919.
2. I've fixed all lint errors on python files but there are ones on the cpp files on the ZeusRendezvous. I took a look at them, and I don't want to fix the linter errors right now for 2 major reasons:
1. Some of them are more than formatting changes (e.g. std::move vs pass by value) and I don't want to introduce bundled changes with the move
1. The old rendezvous code (the one we forked from in caffe2/fb) has the same problems and I think its better for us to deal with this when we deprecate caffe2/fb/rendezvous in favor of the one in torchelastic -T86012579.
Test Plan:
```
buck test mode/dev-nosan //caffe2/torch/distributed/elastic/utils/test/...
buck test mode/dev-nosan //caffe2/torch/distributed/elastic/utils/data/test/...
buck test mode/dev-nosan //caffe2/torch/distributed/elastic/rendezvous/test/...
buck test mode/dev-nosan //caffe2/torch/distributed/elastic/rendezvous/fb/...
buck test mode/dev-nosan //pytorch/elastic/torchelastic/...
```
\+ Sandcastle
Reviewed By: H-Huang
Differential Revision: D26718746
fbshipit-source-id: 67cc0350c3d847221cb3c3038f98f47915362f51
