Print all ops in model converter
Summary:
It will be convenient to print ops names when converting the model in xplat.
This diff moves export_opnames to export_module.cpp so it can be used in xplat (caffe2:optimize_for_mobile and caffe2:torch_train). This function was in caffe2/torch/csrc/jit/serialization/export.cpp. I tried to create a target to include this file but it involves too many ONNX deps and I cannot get it to work.
Test Plan: local test, verified op names are printed
Reviewed By: iseeyuan
Differential Revision: D20961557
fbshipit-source-id: 293569081b29c263c1c441df7a63838a81560ce9
