Improve support of collections

[fedorov]

Add a table with the description, summary, deep link for collections (original and analysis).

[pieper]

I would like to be able to get the same collection summary that is in the IDC collections page and ideally any other information about the collection, like publications that describe the data collection, the patients, etc. This would be so that I can use it for context for LLM based cohort selections.

[fedorov]

The indices (tables) are now available in idc-index-data. What remains to be done is to overhaul how indices are discovered and exposed to the user in idc-index, and to leverage the schemas that are now included to generate documentation of the indices and connections among the tables.