CLN: clean-up test on addition of series/frames
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Cleanup in ``pandas/tests/arithmetic/test_numeric.py``.
- Split ``test_arith_ops_df_compat`` into ``test_add_series`` and ``test_add_frames``.
- Parametrize tests.