[feature] Improve OceanDataCatalog representation in notebooks

[oj-tooth]

Improve the html representation of OceanDataCatalog instances in Jupyter notebooks.

• Add new __repr__ and __repr_html__ methods to OceanDataCatalog class.
• Add item_summary() and collection_summary methods to OceanDataCatalog class.
• Update OceanDataCatalog unit tests.

Relevant Modules

• OceanDataStore/data_catalog.py
• OceanDataStore/tests/test_data_catalog.py