Optimize datapackage cache operations

[KScl]

• The result of datapkg_cache.get("games", Json::objectValue) is always going to be the same; however with a datapackage cache of a significant size, this repeatedly causes a lengthy copy operation for every single game in the multiworld. This results in a significantly long delay on startup in big asyncs with a wide variety of games, even when the datapackages all match. Splitting this operation up like this makes checking for outdated game datapackages significantly faster (near instant).
• There's no point in calling parseDataPkg() early if there are still outdated games we haven't received datapackages for yet, all the work it does will just be overwritten later. Saving this operation until the end and only calling it once speeds up fetching new datapackages significantly, without changing functionality at all.

[N00byKing]

Thanks!