issue: ENG-5766
MessageStore looks like this:
export type MessageStore = {
+messages: { +[id: string]: RawMessageInfo },
+threads: MessageStoreThreads,
+local: { +[id: string]: LocalMessageInfo },
+currentAsOf: { +[keyserverID: string]: number },
};messages, local and threads are filtered by updateMessageStoreWithLatestThreadInfos/processMessageStoreOperations based on what threads were removed by thread reducer. I only need to update currentAsOf.