TST: categorical reindex with added categories
- [x] closes #42424 
- [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
- [ ] whatsnew entry

The bug is specifically in the Interval index. The error arises in the example code from the issue while reindexing the categorical index with another categorical index(with new categories). 

The test (test_cut_with_nonexact_categorical_indices)  from PR [42425](https://github.com/pandas-dev/pandas/pull/42425) implicitly works in a similar way.
 
