[release] 0.57.3 - Bug fix grpc reconnect and add more loggings (#420)

### New Features
- Expose grpc metrics

  ### Fixes
- Fix behavior that when grpc is reconnected to SFP, we sometimes don't
cancel background polling job





>Included In This Release
>- cb2d9e5 kat-statsig
>   - grpc ob (#419)
>- b5f2573 kat-statsig
>   - move fallback class (#418)

Author: xinlili-statsig

statsig/version.py

@@ -1 +1 @@
-__version__ = '0.57.2'
+__version__ = '0.57.3'