[feature] Support creating STAC Items using hierarchical Icechunk stores.

[oj-tooth]

Support the Creation of STAC Items in the NOC STAC using Hierarchical Icechunk Stores.

Actions

• Add group parameter to utility function create_item_from_icechunk_asset()
• Update id naming convention in STAC for Items pointing to individual groups in a hierarchical Icechunk repo.
• Refactor OceanDataCatalog open_dataset() to trigger use of group parameter where a hierarchical Icechunk repo is opened.
• Support use of open_repo() with hierarchical Icechunk repos.