Refactor existing stats code

Legacy statistics

• Raw stats: Load stats from beginning of GALILEO redesign
• Daily stats: Load legacy daily stats from 1995-10 to ???
• Monthly link and login stats: Load legacy stats from 1995-10 to ???
• Monthly vendor stats: Load legacy monthly stats from 1995-10 to present

???: In other words, we could load legacy daily and monthly stats to the "present" (2024-08), or we could load the legacy stats up until the beginning of GALILEO redesign and then run new load processes to load from the raw stats.