[web] Include stateVersion in web PlatformDetails

Summary:
We don't actually seem to ever use stateVersion on the keyserver... but figured it would be good to include it for consistency with native.

Depends on D8063

Test Plan: Flow

Reviewers: michal, kamil

Reviewed By: kamil

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D8064