Resolving Index Resetting for tz_localize
- [x] closes #43080 
- [x] tests added / passed
   I have added a test function `test_series_tz_localize_matching_index`  in `test_tz_localize.py`
- [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
   Index of the original series is preserved while converting `categorical` data to `datetime`
