Consider doing something about WG, GG, the other GG, and _G

They are completely separate entities but have a similar role and extremely similar name, see https://beyond-all-reason.github.io/spring/articles/wupget-communication

Caveats:
* short names are very convenient
* `_G` seems to be a general Lua convention
* would need buy-in from existing games (since technically it's 100% gameside even if everybody just uses whatever basecontent does)

Start with the linked wupget-communication article and compare the roles of WG, GG, the other GG, and _G. This issue needs an agreed naming proposal and buy-in from existing games before implementation; done would mean a settled, compatible direction rather than an isolated code change.

Written by the indexing model from the issue text.