Part of [[ https://linear.app/comm/issue/ENG-5842/delete-old-device-list-attributes-after-migration | ENG-5842 ]].
This diff removes almost all code that referenced "devices" attribute in users table. The code left is not nice, further refactors are done in subsequent diffs.
The only part left is adding devices to the list, which is done separately in D10698 //(I had to reverse diff order to make CI pass)//