BUG: Fix assert_series_equal for categoricals with nulls and check_category_order=False (#62008)
### Description
This PR fixes an issue where `pd.testing.assert_series_equal` fails when comparing Series with categorical values containing NaNs when using `check_category_order=False`.

### Problem
When using `left.categories.take(left.codes)` for comparing category values, null codes (-1) were not handled correctly, causing incorrect comparisons.

Please let me know if my approach or fix needs any improvements . I’m open to feedback and happy to make changes based on suggestions.

Hi @mroeschke
This PR fixes an issue where pd.testing.assert_series_equal fails when comparing Series with categorical values containing NaNs when using check_category_order=False.

I'd really appreciate it if you could take a look and provide feedback .
Please let me know if anything needs to be improved or clarified.

Thanks! Hi @jorisvandenbossche,
Could you please review this PR and let me know if any changes are needed.
Also,I want to ask if the is issue already assigned to someone should I continue working on it or leave it to the current assignee?
Thanks!