Enhance cpu support on gloo based multi-nodes mode. (#11330)
Summary:
1. Add some gloo communication operators into related fallback list;
2. Work around to avoid compiling errors while using fallback operator whose CPU operator inherits from 'OperatorBase' directly like PrefetchOperator;
3. Add new cpu context support for some python module files and resnet50 training example file.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/11330
Reviewed By: yinghai
Differential Revision: D13624519
Pulled By: wesolwsk
fbshipit-source-id: ce39d57ddb8cd7786db2e873bfe954069d972f4f
