[web] Add PickledOLMAccounts to Redux CryptoStore
Summary:
We need to pickle (ie serialize) the OLM accounts so we can eg sign messages. In this diff we add the PickedOLMAccounts to the Redux CryptoStore type.
NOTE: We aren't actually populating the fields yet, just adding them.
Depends on D6881
Test Plan: This should be a noop.
Reviewers: ashoat, tomek, marcin
Reviewed By: ashoat
Differential Revision: https://phab.comm.dev/D6882