BUG: nlargest/nsmallest does not act in accordance with documentaion
- [x] closes #42997 
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

nsmallest/nlargest are now consistent with x.sort_values(ascending=False).head(n)/x.sort_values(ascending=True).head(n)
Edit: I've changed test_nlargest_misc(self) in \tests\serie\methods\test_nlargest.py to reflect the fact that Nans are included