[web] Start persisting keyserverStore

Summary:
issue: https://linear.app/comm/issue/ENG-4794/start-persisting-the-keyserverstore
We want to persist the keyserverStore on web, apart from connection and updatesCurrentAsOf fields. updatesCurrentAsOf doesn't have a straightforward defult value - the keyserver returns
the current time or 0 depending on whether the user has accepted the policies. That's why we are using value passed from the keyserver, stored in preloadedState.

Test Plan:
Checked that keyserverStore is persisted - logged the action.payload of rehydrateActionType in redux-setpu.js. Checked that the connceciotn and updatesCurrentAsOf are set to the
values defined in out function of the Transform object. Chekced that is the user has to accept the policies, the value set to updatesCurrentAsOf is 0, and the current time otherwise.
Checked that the application gets populated with data when the user accpest the policies (it doen't happen if the value of updatesCurrentAsOf is set to the current time right away).

Reviewers: michal, kamil

Reviewed By: michal, kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9062