[functorch] share code between test_vmap_exhaustive and test_op_has_batch_rule (#82659)
test_op_has_batch_rule is technically a superset of
test_vmap_exhaustive, but the signal from both are valuable.
This PR also gets rid of a "hack" by adding some more xfails.
Test Plan:
- wait for tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82659
Approved by: https://github.com/samdow
