Part of ENG-4959
Depends on D9265
Depends on D9266
Modify the hashing on the keyserver (for new clients) so that:
- the hashes are generated from data in client-side-schema, so clients don't have to do the conversion
- the stores aren't hashed by stringifying the whole store but instead we generate a hash for each info and merge them using xor (there's a code comment explaining why that is correct)