FIX: Raise errors when wrong string arguments are passed to `resample`
- [x] closes #19303
- [x] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

As a first step, the initial commit just extends the resampling tests so that they fail when a misstyped string argument, e.g. for `label`, passes silently without raising.

I have the fix for the code ready and will commit when the tests have failed once.