[ENH] nargsort handles EA with its _values_for_argsort
-  closes #25439
-  1 test added and 1 test deleted
-  passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
-  whatsnew entry

Presently, `nargsort` can handle EA too. Because `np.asanyarray` turns EA into `np.ndarray`.
https://github.com/pandas-dev/pandas/blob/430f0fd04646a0ab44ccbfbad706dfe22e9fabfe/pandas/core/sorting.py#L264
In this PR, `nargsort` use `EA._values_for_argsort` instead to avoid the `np.ndarray` conversion.