Differential Revision: [D65362160](https://our.internmc.facebook.com/intern/diff/D65362160)
State after this IR:
1. For the tests that require inference IR, they are replaced with ep.run_decomp({}) so export_for_training_run_decomp is sort of redundant but i guess it is still nice that multiple round of retracing still working. In general, we need some auditing to reduce our redundant testing coverages.
2. After this PR landed and not get reverted for a week or so, i will replace the export_for_training calls with export as they are the same thing now.
3. Added more tests to also cover now "deprecated" old IR by patching export to use old export. For reviewers, please look at the internal version.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139511
Approved by: https://github.com/ydwu4, https://github.com/angelayi, https://github.com/avikchaudhuri