Extract arguments to its own file and pass arguments to ios apps (#15413)

Extract arguments to its own file and pass arguments to ios apps (#15413)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15413

In order to pass arguments to the ios app, need to extarct the arguments
to its own file. Also, in the ios app, do not use the benchmark.json, which
parses the arguments.

This is an incompatible change, needs to add hot fix to the tests.

Reviewed By: llyfacebook

Differential Revision: D13523240

fbshipit-source-id: b559cc7f52d8f50ee206a7ff8d7b59292d855197