Expose major version of desktop code to the keyserver

Summary:
This differential exposes major version of desktop code to the keyserver. It is necessary since ability to decrypt desktop notifications deoends on both web
and desktop code. Those two can be out of sync if user doesn't accept desktop app update.

Test Plan:

1. Apply this patch to the keyserver code: https://gist.github.com/marcinwasowicz/33a1d560f092a38d12ad9fa1e88c9eb1
2. Log-in from dev build of desktop app.
3. Use select * from olm_sessions; in MariaDB console.
4. Ensure that no session was created.
5. Update NEXT_CODE_VERSION to 0.
6. Use select * from olm_sessions; in MariaDB console.
7. Ensure that new session was created for cookie id associated with currently logged in user in desktop app.

Reviewers: michal, kamil

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9973