[native/web] add SQL transaction to persisting crypto module

Summary:
Not sure why there was no transaction here, but I think it's better to add this. Mostly because it implies more than one operation (persisting two accounts in two separate calls).

Wondering what @marcin thinks about this change.

Depends on D11720

Test Plan: Play a bit with crypto-related API to make sure it still works.

Reviewers: tomek, marcin

Reviewed By: marcin

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11721