Improve control server fetching to persist lastFetched data through restarts

[seejdev]

#966 introduces launcher's ability to fetch control server data. The update data is cached in-memory, which avoids re-fetching updates which have already been applied.

If launcher is restarted, the in-memory cache is lost and all update data will be re-fetched and re-applied. Before enabling control server features at scale, we should enable launcher to record and persist update data to disk, and reload them into the in-memory cache after restarts so we can avoid the unnecessary K2 requests involved in re-fetching.

Relates to #935