Refactor `test_foreach.py` (#107869)
## Summary
- Change the default of `supports_autograd` and `supports_forward_ad` of `ForeachFuncInfo` to `True`
- Add `test_zero_size_tensor_inputs` to make sure that foreach functions can handle 0-size Tensor inputs
- Add `test_parity` to check the consistency between outputs of foreach and for-loop of native function.
- Add `test_autodiff` to check forward-mode and reverse-mode AD
- Keep the corner cases that are not covered by the newly introduced methods
rel:
- #58833
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107869
Approved by: https://github.com/janeyx99
