Add Defog Databases and Questions to SQLite Tests in PyDough

[john-sanchez31]

We need to integrate all Defog databases and their associated questions into the SQLite test suite for PyDough.
This involves:

• Adding the databases to the init_defog.sql script so they can be properly initialized.
• Defining and including the corresponding metadata 2.0 in defog_graphs.json.
• Creating the required test infrastructure (fixtures, helper functions, etc.) for these new databases.
• Adding the GEN, BASIC, and ADV question sets.

List of databases to be implemented:

• Academic
• Advising
• Atis
• Derm Treatment
• Geography
• Restaurants
• Scholar
• Yelp