Fix dynamo tests and re-enable internally (#97937)
Summary:
`:test_dynamo` has been broken for long time internally in Meta. This PR is to fix the broken test and re-enable it internally.
- Using the root `pytest.ini` for pytest
- Decouple tests so that one can be disabled with affecting others
- Temporarily disable the test cases that require additional efforts to fix
**OSS CI doesn't provide test code coverage info. Meta internal test infra does. The value of re-enabling these tests internally is not only to collect test coverage info but help fbcode developers to build/test from fbcode.**
Test Plan:
`buck test mode/dev-nosan //caffe2/test:test_dynamo`
https://www.internalfb.com/intern/testinfra/testrun/7318349540623516
Differential Revision: D44325238
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97937
Approved by: https://github.com/ezyang
