BREAKING CHANGE: `token` attribute of OAuth2Auth credentials used to be a dict containing both access_token and refresh_token, given that may cause confusions, now we replace it with access_token and refresh_token at top level of the auth credentials
PiperOrigin-RevId: 750346172
* Move unit tests to root package.
* Adds deps to "test" extra, and mark two broken tests in tests/unittests/auth/test_auth_handler.py
* Adds github workflow
* minor fix in lite_llm.py for python 3.9.
* format pyproject.toml
