Re-architect `lookup` table (yet again!)

[bpblanken]

Re-architect the lookup table:

• One large table with project_guids kept as is, and project_stats migrated to an array of structs (rather than an array of arrays), where each struct is the sum of the ref_samples, het_samples, hom_samples for a project.
• A lookup table for every project, with a family_guids global and a project_stats array of structs, each index representing a family.
• Pipeline logic to update both the project lookup table and the large lookup table whenever a project is loaded.
• Airflow logic to make sure that the lookup table but not the project lookup tables are copied to ssd.
• Seqr logic to read the new lookup table format.

[lynnpais]

Wouldn't need to be done if we were to change the backend.