ENH: Add argmax and argmin to ExtensionArray
-  closes #24382
-  tests added
-  passes `black pandas`
-  passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
-  whatsnew entry

The methods added in this PR ignore `nan` ,i.e., `skipna=True`. The existing `categorical.min` return `nan` if `categorical` contain any `nan`. This behavior is expected in `test_min_max` (tests/arrays/categorical/test_analytics.py). 