CLN: de-duplicate reindex/align code
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

> FAILED pandas/tests/reductions/test_reductions.py::TestSeriesReductions::test_empty_multi[sum-0.0]

on AM unrelated ResourceWarning > unrelated ResourceWarning

yep started seeing that