Announce currently active "daily challenge" playlist to clients

[bdach]

• Depends on Implement creating rooms for queued beatmaps for "daily challenge" system osu-web#11204 for the DB tables
• Depends on Add client/server models & operations for "daily challenge" feature osu#28194 for the models

This adds a DailyChallengeUpdater that polls the database every minute (interval obviously negotiable) to check whether the current active "daily challenge" room changed, and announces that to all clients if it did.

Additionally, on connection to MetadataHub, the metadata hub sends the current "daily challenge" info to the newly-connected client using state stored in the DailyChallengeUpdater.