Enable single graph sharing between multiple threads for onnxifiop (#16047)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16047
Implements single thead safe map enabling sharing of generated graph between
different ops.
Added model_id to every onnxified op to help create a unique id in the map.
Some formatting fix.
Reviewed By: yinghai
Differential Revision: D13663927
fbshipit-source-id: 27417e8fe752fdd48abb6a87966cd76d592e1206
