- Add optional `limit` parameter to the `search` function in catalog.py
- Implement new `describe_catalog` function to get column information of a catalog
- Update unit tests to include the new parameter and test the new function
- Minor formatting improvements in docstrings and test cases

- Introduce new `all_catalog_names()` function in catalog.py to fetch available catalog names
- Enhance `is_valid_datetime_format()` to accept both basic and ISO datetime formats
- Add corresponding unit test for `all_catalog_names()`
- Comment out slow integration tests in level0/level1 test files