BUG in Series.interpolate: limit_area/limit_direction kwargs with method="pad"/"bfill" have no effect
- [x] closes #26796
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Picking up #31048