Add logging for dynamic rendezvous (#61822)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61822
Added scuba logging to the following files:
- dynamic_rendezvous.py
- c10d_rendezvous_backend.py
NOTE: This diff introduces the use of python's inspect module to easily allow for obtaining the calling method name and filename when logging. This module can mess with python's garbage collector, so special care was taken to never store references to results from inspect.stack() longer than absolutely needed.
Test Plan:
The following tests can be run.
```
buck run mode/dev-nosan //caffe2/test/distributed/elastic/rendezvous:c10d_rendezvous_backend_test
```
```
buck run mode/dev-nosan //caffe2/test/distributed/elastic/rendezvous:dynamic_rendezvous_test
```
```
buck run mode/dev-nosan //caffe2/test/distributed/elastic/events:lib_test
```
Reviewed By: aivanou
Differential Revision: D29643774
fbshipit-source-id: f10cd5ebf8f6860856267bc2483c0b85faacb0fd
