Table to store data from UserStore in SQLite.
Column types are based on Flow types.
Some time ago @atul suggested to make this table key-value with data in JSON - I still think for some stores it's beneficial but here I decided to make more datailed data representation. Making key-value doesn't speed things up that much, and I think at some point we might want to have easy access to user data from C++/Rust (for example avatar to show more detailed notif).
EDIT: actually that was a bad assumption, avatar can have multiple types which force us to use JSON anyway which means we will not gain anything, and the amount of C++ code is reduced a lot, that being said proceeding with a simple key-value table.
Depends on D9902