issue: ENG-6484
fullStateSyncActionType always concerns only one keyserver. It is a "specific" action. It has a keyserverID in the payload.
reduceIntegrityStore -> we should not clear the whole store, only remove the threads related to this keyserver
reduceThreadInfos -> we shouldn't remove all threads, only the threads related to this keyserver
reduceCurrentUserInfo -> it should not change currentUserInfo for clients not relying on authoritative keyserver
reduceUserInfos -> it shouldn't be removing user infos for clients not relying on authoritative keyserver