Update the backend interface (#1384)
Summary:
This PR updates the flow of argument parsing. It parses all the backend arguments before initializing the model.
This makes model developers no need to worry about arguments in the backend.
Later, we will move fuser and tensorrt backends to the same format.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1384
Reviewed By: erichan1
Differential Revision: D42823999
Pulled By: xuzhao9
fbshipit-source-id: 7a4c9abe916f2724cf9764bcd1b81180fab60be5
