[HUGE ISSUE] rewrite backend to use unique location identifiers

[jeffzyliu]

Description

Big issue--RD spelling is constantly out of sync. Solution--have RD unique identifiers.
Applies somewhat to county too with FIPS--this makes things more robust, and enables functionality such as multi-state-selections.

To do this, schemas need to change, and also indices. Instead of year state location, maybe year uniqueID? or year state uniqueID? not super clear honestly.

Frontend will need some rewriting to be compatible with database indexing changes etc, but it will make mapbox much cleaner and not buggy.

Finally the DBs will need to be re-seeded from scratch, which will take a lot of data cleaning to do for pre-2021 summarized county/rd data as well as cleaning county and RD spots to agree with the unique identifiers.

Type of Issue

• New feature
• Bug fix
• Documentation update

[jeffzyliu]

reconnect frontend to use the most recent mapbox tileset after this is done, because that tileset is going to need the RD identifiers