CommonClient: request datapackage per-game

[Berserker66]

What is this fixing or adding?

Updates the reference clients to request one game's datapackage at a time. While it can handle very large packets and doesn't really need it, it makes it slightly more future proof and might inspire someone to copy it into their library as well.

How was this tested?

By making a client forget it has a cache.

If this makes graphical changes, please attach screenshots.

[Jarno458]

Does this add any benefit?
await self.send_msgs([{"cmd": "GetDataPackage", "games": [game_name]} for game_name in needed_updates])
since its all passed as 1 array to send_msgs, it all still send as part of the same websocket message right?

[Berserker66]

Send as one message, yes. But received as several.